第19题: [单项选择]From the passage we know that "the greenhouse effect" is an effect in which ______. A. low temperatures are created by using a house B. the house is made green in order to keep heat C. heat is prevented from escaping outside D. everything is kept green in a house 参考答案:C 答案解析:从文章第二自然段开头,我们可以看出,由于the green house effect(温室效应)致使the gas prevents the escape of heat into outer spa