Water, （） enough, can change into vapour quickly. A: when heated B: heating C: though to be heated D: when is heated

Petrol<br/>has a low boiling point; if a little is poured into the hand it soon<br/>changes into ______. A: veil B: vapour C: vacuum D: velocity

Which of the following is not true about the greenhouse effect? A: Water vapour belongs to greenhouse gases. B: The greenhouse effect is a bad thing. C: Carbon Dioxide is the main greenhouse gas. D: The melting of the polar ice caps will accelerate because of the greenhouse effect.