12. A 【解析】考查介词。work for意为＂为......努力＂。作者认为母亲正在毁掉自己为之努力的一切。A选项正确。

II.阅读理解

　　【文章大意】本文是一篇记叙文。《探索频道》邀请史上获得奥运金牌最多的游泳名将迈克尔·菲尔普斯与大白鲨进行了一场百米游泳对决，最终菲尔普斯以两秒之差输给大白鲨，但却因为视频中的鲨鱼不是真的而导致一些粉丝有些失望。

1. D 【解析】推理判断题。根据第一段的when he was approached by the Discovery Channel to help kick off Shark Week和最后一段的Given that it was the highest-rated Shark Week special in the program's 29-year history, they surely succeeded.可知《探索频道》邀请菲尔普斯的目的是帮忙宣传他们的节目《鲨鱼周》，吸引更多人关注该节目。故选D 项。

2. A 【解析】推理判断题。根据第二段的While the swimmer's time of 18.7 seconds was enough to beat the reef shark by 0.2 seconds, he fell behind the hammerhead...和第五段的... he was no match for the great shark, which clocked 36.1 seconds可推知游得最慢的是the reef shark。故选A项。

3. D 【解析】推理判断题。根据最后一段的Some fans were disappointed that Phelps did not race a live shark in the ocean, although that would have been dangerous for the swimmer.可推知一些粉丝们原以为菲尔普斯会和一条真正的大白鲨在大海里比赛。故选D项。

4. C 【解析】标题归纳题。全文大意是《探索频道》邀请史上获得奥运金牌最多的游泳名将迈克尔•菲尔普斯与大白鲨进行了一场百米游泳对决，最终他以两秒之差输给大白鲨，但却因为视频中的鲨鱼不是真的而导致一些粉丝有些失望，由此可知最佳题目应为菲尔普斯与大白鲨的游泳比赛。故选C项。

III.语法填空