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Grammar Test - Days of the week 
Grammar Test - Pronouns 
Grammar Test - needn't/don't need 
Grammar Test - and/but 
Grammar Test - Past Simple/Past Perfect 
Grammar Test - arrive/get/reach 
Grammar Test - Modals 
Grammar Test - Phrasal Verbs - Work 
Grammar Test - _or/_er 
Grammar Test - Order of Adjectives 
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The algae develops the beta carotene pigment when the lake water reaches a salinity level greater than that of sea water and when adequate light and temperature conditions are achieved.