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Questions 23 to 25 are based on the conversation you have just heard.
23.What are the speakers mainly discussing?
【解析】[B]从对话的开头就可以看出astronauts have made commercial products in space，主要讨论的就是在太空中生产的产品。
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.从可作癌症研究的用途中能看出可作医学研究。
25.According to the man, why did astronauts make beads in space?
【解析】[D]因为地球引力作用使球不纯圆。The beads on earth are distorted, not exactly round.在太空中做的球会非常圆。
