People           about what our future will look like for thousands of years.

have been wondering

wonder

wondered

will wonder

考查动词时态。句意：数千年以来人们一直想知道我们未来是什么样子。根据时间状语 for thousands of years可知，描述从过去开始一直持续到现在的动作，用现在完成进行时。故选A项。

They elected him          captain of the team for         second time.

the; a

a; the

a; a

/; a

考查冠词的用法。句意：他们再次选他当队长。职位，官衔前面不加冠词，a second time表示“又一次，再次”；the second time表示第二次（顺序）。故选D项。

With a lot of difficult problems           ,he feels like a cat on  hot bricks.

to settle

being settled

settling

settled

考查非谓语动词。句意： 因为有一大堆难题要解决，他感觉像像热锅上的蚂蚁。本句with +名词+to do sth,动词不定式表示的动作尚未发生或当时看来尚未发生。本句表示“因为有一大堆难题要解决”。故选A项。

The sunlight is white and blinding,           hard-edged shadows on the ground.

throwing

being thrown

to throw

to be thrown

考查非谓语动词。句意：阳光炽白炫目，在地上投下浓重的阴影。主语The sunlight和throw是主动关系，因此要用现在分词表主动，此处是现在分词短语作状语。故选A项。

Don't forget            the letter for me when you pass  by the post office.

post

to post

posted

posting

考查不定式作宾语。句意：你经过邮局时别忘了替我寄这封信。forget to do sth忘记要做某事；forget doing sth 忘记做过某事。根据句意表示事情已经发生。故选B项。