Grammar Test - have/has

Oxygen is a safe, non explosive gas when handled correctly. However, any material that is already burning will burn much faster and hotter in an oxygen enriched environment, so the following precautions should be observed when you use home oxygen. Keep the oxygen at least 3 metres from any open flame or heat source, such as candles or a gas stove, or from anything that could cause a spark. Do not smoke or let anyone else smoke near the oxygen equipment. Avoid using anything flammable near the oxygen, including petrol, cleaning fluid, and aerosol cans or sprays such as fresheners or hairspray.