第9题:[单项选择]<br><br><br/>A.at<br/>B.on<br/>C.with<br/>D.for<br/>参考答案:A 答案解析:[精解] 固定词组题。at the beginning of在……开始的时候;in the beginning不加介词of,表示在开始时,答案应是[A]。
第17题: [填空题]The Greenhouse Effect is generally believed to come from the ______in the atmosphere. 参考答案:buildup of carbon dioxide gas 答案解析:本题根据第二个黑色小标题下第四段第一句而设,“The Greenhouse Effect,also referred to as global warming,is generally believe