【正确答案】 B

【答案解析】[听力原文]19-22
M: Did you know that astronauts have made commercial products in space?
W: No, I wasn't aware of that. What kind of products?
M: Tiny plastic beads with a little hole through it.
W: Tiny balls? Do you mean to tell me that astronauts have nothing better to do than make jewelry beads in space? It seems to me they could make more useful things out there.
M: Oh, but these little balls aren't for jewelry. They can be used for scientific purposes to conduct cancer research .
W: That sounds better, but why make such objects in space rather than on earth?
M: Because earth gravitational pull affects the beads. They produced on earth are distorted, not exactly tumid. The ones made in space are precisely round.
W: Sounds reasonable.
19. What are the speakers mainly discussing?

主旨题。对话主要是围绕着在宇宙中制造的产品展开的，因此答案应为B)。

【正确答案】 A

【答案解析】[听力原文]
According to the conversation, what is the likely use for the beads?

判断题。问题是“这些小球可能用来做什么用?”从男子的第三句话中很明显就排除了D)。接着又说它们是用来进行癌症研究的。因此答案为A)。

【正确答案】 D

【答案解析】[听力原文]
According to the man, why did astronauts make the beads in space?

事实题。对话的最后提到了在宇宙中制造的球更圆。答案为D)。

【正确答案】 C

【答案解析】[听力原文]
What material were the beads made of?

细节题。在对话的第三句中说到“tiny plastic beads”，所以应选C)。