A、 Knocking the air cushion overboard.
B、 Putting out the sea anchor.
C、 Diving into the sea to try to fetch the air cushion.
D、 Putting out the sea anchor clumsily so that it became entangled.

【正确答案】 C

【答案解析】解析：推断题。根据听力短文中I lowered the sail，put out the sea anchor and dived in to fetch it可知那天“我”落帆、抛锚、跳入水中抓气垫。接着短文又提到“结果船却撇下我自己行驶，尽管我游泳很好，还是没有赶上”。由此可推断，那天“我”做得最傻的事就是跳人水中找气垫。因此，正确答案是C。

A、 He swam faster than he had ever swum before.
B、 The sea anchor disentangled itself.
C、 He abandoned the air cushion.
D、 The sail came down.

【正确答案】 B

【答案解析】解析：推断题。根据听力短文可知，作者看到船放慢了速度，并且锚上的线也不缠在一起了，可以推断这就是作者赶上船的原因。只有B选项符合。因此，正确答案是B。

A、 He got exhausted in trying to catch up with the boat.
B、 It was his last trip.
C、 The boat slowed down.
D、 He had not been so good.

【正确答案】 A

【答案解析】解析：细节题。根据听力短文I was exhausted and swore it was the last dip I would take on the journey．可知作者是因为很累才不愿意下海。因此，正确答案是A。