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。

Tom looks so pale today. He ______ ill.

must be

had to be

should be

shall be

[翻译]汤姆看起来脸色不好，他一定生病了。[解析] A 试题解析：情态动词must表示推测。题目中表示肯定的推测。

It was fortunate that Jack narrowly escaped             in a traffic accident last month.

killing

being killed

to be killed

 to kill

考查非谓语动词。句意：杰克上个月在交通事故中死里逃生，真是幸运。固定表达escape doing sth.逃离做某事。此处Jack与kill之间是被动关系，应该使用动名词的被动语态，用being killed。故选B项。

Daniel has undertaken to keep the secret, so he won’t tell anyone even though ______.

asked to keep

to be asked

to ask

asked to

考查省略和过去分词。句意：丹尼尔答应保守这个秘密，所以即使问他也不会告诉任何人。此处是even though引导的让步状语从句，从句主语和主句主语都是he，和ask之间是被动关系，相同的主语和be动词可以省略，所以这里是过去分词作状语，且ask sb. to do sth.可以省略与前面相同的部分，只留下动词不定式符号to。故选D。