A、 The anatomy of sea cucumbers.
B、 How sea cucumbers protect themselves.
C、 How to catch a sea cucumber.
D、 The history of sea cucumbers.

【正确答案】 B

【答案解析】解析：题目问的是对话的主旨是什么。由定位句可知本对话主要是关于海参的自我防卫机制的。故选B。

A、 By expelling its organs.
B、 By moving quickly.
C、 By organizing itself.
D、 By hiding itself.

【正确答案】 A

【答案解析】解析：题目问的是海参是如何保护自己的。由定位句可知，海参通过喷出自己的内脏器官来保护自己，故选A。

A、 There were too many organs in the sea cucumber.
B、 He didn' t understand why another animal would want to eat the sea cucumber.
C、 He didn't understand what defense meant.
D、 He didn' t think it made sense to lose organs to protect the body.

【正确答案】 D

【答案解析】解析：题目问的是男士为什么感到很困惑。由定位句可知，男士认为海参通过喷射内脏器官保护自己是说不通的，故选D。

A、 It spit up its organs.
B、 It lives on the bottom of the sea.
C、 Its organs grow back quickly.
D、 It has no spinal column.

【正确答案】 D

【答案解析】解析：题目问的是我们是如何分辨出海参是原始动物的。由定位句可知，海参是原始动物因为其没有脊柱。故选D。

A、 They can cut themselves in half and survive.
B、 They are spinal animals and thus need very little for life.
C、 They give up their internal organs to confuse their attacker.
D、 Their organs are easy to grow back.

【正确答案】 A

【答案解析】解析：题目问的是关于海参，哪一项是不正确的。由定位句可知，其他的一些原始的无脊柱虫子可以被切掉一段后还继续存活，但并不是说海参也可以，故选A。