It was last night ________ I saw the comet.

the time

when

that

which

强调句的结构是：It＋be＋强调部分＋that(who)＋主谓句。强调句的连词只有两个，that和who。当强调的部分是人，且为句子的主语时，才用“who”，其余用that。因此选C。

It is well-known that crack cocaine is a powerful             drug and users become           to it much more easily if they smoke it.

addicted; addict

addictive; addict

addicted; addictive

addictive; addicted

考查形容词辨析。众所周知可卡因是一种强大的令人上瘾的毒品，如果使用者吸了它更容易上瘾得多。addicted上瘾的，着迷的；addict"shi使沉迷；使上瘾”是动词；addictive “使成瘾的，令人沉迷的”。第一空表示“令人上瘾的”用addictive，故排除A，C项；become addicted to “对....上瘾”，第二空填addicted。故选D项。

It was not until 1920 ___ regular radio broadcasts began.

when

which

that

since

此题考查强调句。句意为：直到1920年，常规的电台才开始。这句话把it is/was和that去掉后，仍是完整的一句话，因此我们可以知道这是一个强调句，而且是对not...until“直到...才”的强调。结构是：it is/was+not until+其他成分。故选:C.

She reading

She reads

To read

Reading

考查时态以及省略。句意：—Joan正在做什么？—在房间里看报纸。根据句意说明描述的是现在正在发生的事情，所以使用进行时的时态，是对what is Joan doing?的回答。回答完整应该是she is reading...，此处省略了she is，故D正确。

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。

If you want to catch the first bus you'd better         for the bus station immediately.

set up

set about

set down

set off

考查动词短语辨析。句意：如果你想赶上第一班公交车，你最好马上动身去车站。A. set up建立；B. set about开始做.....;C. set down 记下；D. set off 出发，动身。结合上文If you want to catch the first bus you'd better可知此处指“动身，出发”，应用set off。故选D项。