Questions 23 to 25 are based on the conversation you have just heard.

　　23.What are the speakers mainly discussing?

　　【解析】[B]從對話的開頭就可以看出astronauts have made commercial products in space，主要討論的就是在太空中生產的產品。

　　24.According to the conversation, what is a likely use for the beads?

　　【解析】[A]They can be used for many scientific purposes, from conducting cancer research to calibrating microscopes.從可作癌癥研究的用途中能看出可作醫學研究。

　　25.According to the man, why did astronauts make beads in space?

　　【解析】[D]因為地球引力作用使球不純圓。The beads on earth are distorted, not exactly round.在太空中做的球會非常圓。

來源:可可英語 http://www.ccdyzl.cn/cet4/201006/105658.shtml