C. Under; solved D. With; solved

【答案】D

【解析】

【详解】考查固定搭配和时态。固定搭配with the help of在...的帮助下；work out计算出，制定出；work on从事于；solve解决。句意：在老师的帮助之下，那位擅长于数学的学生很快就解决了那道数学题。结合句意可知句子用一般过去时态，故选D。

3.I went to see a film _____ last year.

A. every three weeks B. every third weeks

C. each three weeks D. each third week

【答案】A

【解析】

【详解】考查固定用法。句意：去年我每三个星期去看一场电影。表示"每......"或"每隔"常用every,不用each。every three weeks/every third week"每隔三周"，故选A。

4.Mr. Wang made up his mind to devote all he could _____the poor people in the flooded area.

A. help B. to help

C. helping D. to helping

【答案】D

【解析】

【详解】考查固定搭配。句意：王先生决心尽他所能帮助灾区的穷人。此题中包含固定短语devote...to，其中to 为介词，后面应接定名词。动词devote后接的宾语为all，all又为先行词，后又包含一个定语从句：he could (do)。此题很容易误以为could后应接动词原形，而易选为A。答案为D。

5.--I think he is taking an active part in social work.

--I agree with you ____.

A. on the way B. in a way

C. by the way D. in the way

【答案】B

【解析】

【详解】考查介词短语辨析。on the way在途中，即将；in a way在某种程度上；by the wa