【答案解析】[解析] 再现题。文章指出Dry ice is made by freezing a gas．所以答案是D。 [听力原文] Questions <17>-<20> Can you imagine ice that does not melt and is not wet.'? Have you ever heard of dry ice? Dry ice is made by freezing a gas. It is quite different from ordinary ice, which is simply frozen water. Dry ice was first manufactured in 1925. It has fulfilled the hopes of its inventor. It can be used for making artificial fog in the movies. When steam is passed over dry ice, a very dense vapor rises. It can also be used for destroying insects in grain supplies. It is more practical than ordinary ice be cause it takes up less space and is 142 degrees colder. Since it turns into steam instead of melting in to water, it is cleaner to use. For these reasons it is extremely popular, and many people prefer it to ordinary ice.
【正确答案】
A
【答案解析】[解析] 再现题。文章中指出It can be used for making artificial fog in the movies． When steam is passed over dry ice，a very dense vapor rises．因此答案选A。
【正确答案】
C
【答案解析】[解析] 再现题。文章中指出Since it turns into steam instead of melting into water，it is cleaner to use．故选C。
【正确答案】
A
【答案解析】[解析] 再现分析题。文章中指出Dry ice was first manufactured in 1925．结合年代的表示方法，可知答案是A。