（  ）11.The number of smokers，_____is reported，has dropped by 17 percent in just one year.

A.a

B.which

C.what

D.as

11.D【解析】句意：正如所报道的那样，吸烟者的数量仅一年就减少了17%。这是含有非限制性定语从句的复合句，空缺的词为关系代词，故排除A、C。as引导的非限制性定语从句位置灵活，可以放在句首、句中、句末。这里的关系代词指代的是“the number of smokers has dropped by 17% in just one year”这一整句，且as is reported是常用表达法。故选D。

（  ）12._____more about Chinese culture，Jack has decided to take Chinese folk music as an elective course.

A.Learn

B.Learned

C.To learn

D.To be learning

12.C【解析】Jack与learn之间为逻辑上的主动关系，且表示目的，故用不定式作目的状语。句意：为了更多地了解中国文化，杰克已经决定把中国民间音乐作为选修课程。

（  ）13.Jane is in a hurry because the train to the airport leaves_____half an hour.

A.By

B.in

C.for

D.until

13.B【解析】此处in half an hour意为“半个小时以后”。句意：Jane很着急，因为去机场的火车半小时后出发。根据句意选B。

（  ）14.Jim_____his strict father，for he failed in the exam once again.

A.didn’t dare to see

B.not dare see

C.dared not to see

D.dare not saw

14.A【解析】dare既可作情态动词，也可作实义动词。作实义动词后跟不定式，作情态动词后跟动词原形。句意：Jim不敢见他严厉的父亲，因为他又一次考试不及格。

（  ）15.If you have any doubts about your health，you’d better  your doctor at once.

A.Convince

B.consult

C.avoid

D.affect

15.B【解析】convince“说服，信服”；consult“咨询，参考”；avoid“避免”；affect“影响”。句意：如果你对你的健康有疑问，最好咨询你的医生。