The old rules have to be          because they only applied to the circumstances that existed when they were made a hundred years ago.

developed

established

observed

revised

考查动词的辨析。句意：老的规则需要被修改因为它们只适合一百年制定时的状况。A.develop发展；培养；B.establish建立；C.observe观察；D.revise修改，由because they only applied to 可知它只适用于以前，需要修改。故选D项。

If you work hard like this, you will           sooner or later.

give out

break up

break down

fall down

考查动词短语。句意：如果你继续这样辛苦工作的话，你迟早垮掉。A.give out分发 ；B.break up打碎；C.break down垮掉；D.fall down 跌倒。根据句意可知break down符合语境。故选C项。

Mary never does any reading in the evening, ______.

so does John 

John does too

John does not to

neither does John

主句用never，后面的倒装句相应的用nor或者neither，用完全倒装形式表示后者与前者情况相似。

A study shows the students who are engaged in after-school  activities are happier than        who are not.

ones

those

these

them

考查代词。句意：一项研究表明，参加课外活动的学生比不参加课外活动的学生更开心。空格处代词与the students是对应关系，可以用the ones 或者those替代。“them”指代前面提到的复数名词，不能与the students形成对应关系，“these”一般不用定语从句修饰。故选B项。