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must: deduction

  • We can use must lo say that we are sure about something (because it is logically necessary).
      If A is bigger than B, and B is bigger than C, then A must be bigger than C.
      Mary keeps crying. She must have some problem.
      There's the doorbell. It must be Roger.
      'I'm in love. ' 'That must be nice.'
  • In questions and negatives, we use can and can't with this meaning, not must and mustn't.
      'There's somebody at the door. Who can it be?
      It can't be the postman. It's only seven o'clock.'
      What do you think this letter can mean?
  • We use [must have + past participle] for deductions about the past
      (can have in questions and negatives).
      [must/can/can't have + past participle]
      'We went to Rome last month.' 'That must have been nice.'
      I don't think he can have heard you. Call again.
      Where can John have put the matches? He can't have thrown them away.
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  • 'copula1 verbs
  • 'social' language
  • (a) few and (a) little
  • (a)round and about
  • (be) used to + noun or... -ing
  • (Great) Britain, the United Kingdom, the British Isles and England
  • -ing form ('gerund')
  • -ing form after to
  • -ing form or infinitive?
  • abbreviations
  • about to
  • above and over
  • across and over
  • across and through
  • active verb forms
  • actual(ly)
  • adjectives ending in -Iy
  • adjectives without nouns
  • adjectives: order
  • adjectives: position
  • adverbs of manner
  • adverbs: position (details)
  • adverbs: position (general)
  • after (conjunction)
  • after (preposition); afterwards (adverb)
  • after all
  • afternoon, evening and night
  • ages
  • ago
  • all (of) with nouns and pronouns
  • all and every
  • all and whole
  • all right
  • all with verbs
  • all, everybody and everything
  • almost and nearly
  • also, as well and too
  • although and though
  • among and between
  • and
  • and after try, wait, go etc
  • another
  • any (= 'it doesn't matter which')
  • any and no: adverbs
  • appear
  • articles: a and an; pronunciation of the
  • articles: a/an
  • articles: countable and uncountable nouns
  • articles: introduction
  • articles: special rules and exceptions
  • articles: talking in general
  • articles: the
  • articles: the difference between a/an and the
  • as and like
  • as if and as though
  • as much/many ... as ...
  • as well as
  • as, because and since (reason)
  • as, when and while (things happening at the same time)
  • as...as ...
  • ask
  • at all
  • at, in and on (place)
  • at, in and on (time)
  • be + infinitive
  • be with auxiliary do
  • be: progressive tenses
  • because and because of
  • before (adverb)
  • before (conjunction)
  • before (preposition) and in front of
  • begin and start
  • big, large, great and tall
  • born
  • borrow and lend
  • both (of) with nouns and pronouns
  • both with verbs
  • both... and...
  • bring and take
  • British and American English
  • broad and wide
  • but = except
  • by: time
  • can and could: ability
  • can and could: forms
  • can with remember, understand, speak, play, see, hear, feel, taste and smell
  • can: permission, offers, requests and orders
  • can: possibility and probability
  • close and shut
  • come and go
  • comparison: comparative and superlative adjectives
  • comparison: comparative and superlative adverbs
  • comparison: much, far etc with comparatives
  • comparison: using comparatives and superlatives
  • conditional
  • conjunctions
  • contractions
  • countable and uncountable nouns
  • country
  • dare
  • dates
  • determiners
  • discourse markers
  • do + -ing
  • do and make
  • do: auxiliary verb
  • during and for
  • during and in
  • each and every
  • each other and one another
  • each: grammar
  • either... or...
  • either: determiner
  • ellipsis (leaving words out)
  • else
  • emphasis
  • emphatic structures with it and what
  • enjoy
  • enough
  • even
  • eventual(ly)
  • ever
  • every and every one
  • except
  • except and except for
  • exclamations
  • excuse me, pardon and sorry
  • expect, hope, look forward, wait, want and wish
  • explain
  • fairly, quite, rather and pretty
  • far and a long way
  • farther and further
  • fast
  • feel
  • fewer and less
  • for + object + infinitive
  • for, since, from, ago and before
  • for: purpose
  • future perfect
  • future progressive
  • future: introduction
  • future: present progressive and going to
  • future: shall and will (interpersonal uses)
  • future: shall/will (predictions)
  • future: simple present
  • gender (masculine and feminine language)
  • get (+ object) + verb form
  • get + noun, adjective, adverb particle or preposition
  • get and go: movement
  • go ... -ing
  • go meaning'become'
  • go: been and gone
  • had better
  • half (of)
  • hard and hardly
  • have (got) to
  • have (got): possession, relationships etc
  • have + object + verb form
  • have: actions
  • have: auxiliary verb
  • have: introduction
  • hear and listen (to)
  • help
  • here and there
  • holiday and holidays
  • home
  • hope
  • how and what... like?
  • if only
  • if so and if not
  • if-sentences with could and might
  • if: ordinary tenses
  • if: special tenses
  • ill and sick
  • imperative
  • in and into (prepositions)
  • in case
  • in spite of
  • indeed
  • infinitive after who, what, how etc
  • infinitive of purpose
  • infinitive without to
  • infinitive: negative, progressive, perfect, passive
  • infinitive: use
  • instead of... -ing
  • inversion: auxiliary verb before subject
  • inversion: whole verb before subject
  • irregular verbs
  • it's time
  • it: preparatory object
  • it: preparatory subject
  • last and the last
  • let's
  • letters
  • likely
  • long and for a long time
  • look
  • look (at), watch and see
  • marry and divorce
  • may and might: forms
  • may and might: permission
  • may and might: probability
  • mind
  • modal auxiliary verbs
  • more (of): determiner
  • most (of): determiner
  • much (of), many (of): determiners
  • much, many, a lot etc
  • must and have to; mustn't, haven't got to, don't have to, don't need to and needn't
  • must: deduction
  • must: forms
  • must: obligation
  • names and titles
  • nationality words
  • need
  • negative questions
  • negative structures
  • neither (of): determiner
  • neither, nor and not... either
  • neither... nor...
  • next and nearest
  • next and the next
  • no and none
  • no and not
  • no and not a/not any
  • no more, not any more, no longer, not any longer
  • non-progressive verbs
  • noun + noun
  • numbers
  • once
  • one and you: indefinite personal pronouns
  • one: substitute word
  • other and others
  • ought
  • own
  • participle clauses
  • participles used as adjectives
  • participles: 'present' and 'past' participles (-ing and -ed)
  • passive structures: introduction
  • passive verb forms
  • past tense with present or future meaning
  • past time: past perfect simple and progressive
  • past time: past progressive
  • past time: present perfect progressive
  • past time: present perfect simple
  • past time: simple past
  • past time: the past and perfect tenses (introduction)
  • perfect tenses with this is the first time..., etc
  • personal pronouns (I, me, it etc)
  • play and game
  • please and thank you
  • possessive with determiners (a friend of mine, etc)
  • possessive's: forms
  • possessive's: use
  • possessives: my and mine, etc
  • prepositional verbs and phrasal verbs
  • prepositions after particular words and expressions
  • prepositions and adverb particles
  • prepositions at the end of clauses
  • prepositions before particular words and expressions
  • prepositions: expressions without prepositions
  • present tenses: introduction
  • present tenses: present progressive
  • present tenses: simple present
  • progressive tenses with always
  • punctuation: apostrophe
  • punctuation: colon
  • punctuation: comma
  • punctuation: dash
  • punctuation: quotation marks
  • punctuation: semi-colons and full stops
  • question tags
  • questions: basic rules
  • questions: reply questions
  • questions: word order in spoken questions
  • quite
  • real(ly)
  • reflexive pronouns
  • relative pronouns
  • relative pronouns: what
  • relative pronouns: whose
  • relatives: identifying and non-identifying clauses
  • remind
  • reported speech and direct speech
  • reported speech: orders, requests, advice etc
  • reported speech: pronouns; 'here and now' words; tenses
  • reported speech: questions
  • requests
  • road and street
  • say and tell
  • see
  • seem
  • shall
  • short answers
  • should
  • should after why and how
  • should and would
  • should, ought and must
  • should: (If I were you) I should ...
  • similar words
  • since (conjunction of time): tenses
  • singular and plural: anybody etc
  • singular and plural: irregular plurals
  • singular and plural: plural expressions with singular verbs
  • singular and plural: pronunciation of plural nouns
  • singular and plural: singular words ending in -s
  • singular and plural: singular words with plural verbs
  • singular and plural: spelling of plural nouns
  • slow(ly)
  • small and little
  • smell
  • so am I, so do I etc
  • so and not with hope, believe etc
  • some and any
  • some/any and no article
  • some: special uses
  • somebody and anybody, something and anything, etc
  • sound
  • spelling and pronunciation
  • spelling: -ise and -ize
  • spelling: -ly
  • spelling: capital letters
  • spelling: ch and tch, k and ck
  • spelling: doubling final consonants
  • spelling: final -e
  • spelling: full stops with abbreviations
  • spelling: hyphens
  • spelling: ie and ei
  • spelling: y and i
  • still, yet and already
  • subject and object forms
  • subjunctive
  • such and so
  • suggest
  • surely
  • sympathetic
  • take
  • take (time)
  • tall and high
  • taste
  • telephoning
  • telling the time
  • tenses in subordinate clauses
  • that: omission
  • the same
  • there is
  • think
  • this and that
  • too
  • travel, journey and trip
  • unless and if not
  • until and by
  • until and to
  • used to + infinitive
  • verbs with object complements
  • verbs with two objects
  • way
  • weak and strong forms
  • well
  • when and if
  • whether and if
  • whether... or...
  • which, what and who: question words
  • who ever, what ever, how ever etc
  • whoever, whatever, whichever, however, whenever and wherever
  • will
  • wish
  • worth ... -ing
  • would
  • would rather
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  • Simple Science

    Destructive Action of Water

    Water:
    The action of water in stream and sea, in springs and wells, is evident to all; but the activity of ground water - that is, rain water which sinks into the soil and remains there - is little known in general. The real activity of ground water is due to its great solvent power; every time we put sugar into tea or soap into water we are using water as a solvent. When rain falls, it dissolves substances floating in the atmosphere, and when it sinks into the ground and becomes ground water, it dissolves material out of the rock which it encounters. We know that water contains some mineral matter, because kettles in which water is boiled acquire in a short time a crust or coating on the inside. This crust is due to the accumulation in the kettle of mineral matter which was in solution in the water, but which was left behind when the water evaporated.

    The amount of dissolved mineral matter present in some wells and springs is surprisingly great; the famous springs of Bath, England, contain so much mineral matter in solution, that a column 9 feet in diameter and 140 feet high could be built out of the mineral matter contained in the water consumed yearly by the townspeople.

    Rocks and minerals are not all equally soluble in water; some are so little soluble that it is years before any change becomes apparent, and the substances are said to be insoluble, yet in reality they are slowly dissolving. Other rocks, like limestone, are so readily soluble in water that from the small pores and cavities eaten out by the water, there may develop in long centuries, caves and caverns. Most rock, like granite, contains several substances, some of which are readily soluble and others of which are not readily soluble; in such rocks a peculiar appearance is presented, due to the rapid disappearance of the soluble substance, and the persistence of the more resistant substance.

    We see that the solvent power of water is constantly causing changes, dissolving some mineral substances, and leaving others practically untouched; eating out crevices of various shapes and sizes, and by gradual solution through unnumbered years enlarging these crevices into wonderful caves, such as the Mammoth Cave of Kentucky.

    FIG. - Showing how caves and holes are formed by the solvent action of water.

    FIG. - The work of water as a solvent.


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