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。

Look! There is         over there. Do you know him?

a 8-year-old boy

an 8-year-old boy

a 8-years old boy

an 8-years old boy

考查形容词和冠词。句意：看！那边有一个8岁的男孩。你认识他吗？空格处为复合形容词作定语，其基本构成形式是：数词+名词（单数）+形容词，并且要用连字符连接，排除C和D项；8发音以元音音素开头，需用不定冠词an修饰。故选B项。

          no bus,we had to walk home.

There was

There being

Because there being

It being

考查独立主格结构。句意：没有车，我不得不走路回家。根据句意，表示“存在”，要用there be 句型；分析句子可知，设空处应用非谓语动词，there be只有主动形式，故用现在分词；因为非谓语动词有自己独立的的主语no bus,所以此处是独立主格结构。故选B项。

You don't have to know the name of the author to find a book. You           find the book by the title.

must

need

can

would

考查情态动词辨析。句意：你不需要知道作者的名字就能找到一本书。你可以按书名找到这本书。A.must必须，一定；B.need 需要；C. can可能；可能；D.would愿意。根据句意可知，此处表示一种客观的可能性，应使用情态动词can。故选C项。

Every evening after dinner, if not ________ from work, I will spend some time walking my dog.

being tired

tiring

tired

to be tired

考查省略句。当状语从句的主语和主句主语一致，且状语从句中有be动词的时候，可以把状语从句的主语和be动词一起省略，本题if后面省略了I am，句意：每天晚上吃完晚饭以后，如果不是很累，我就会花点时间来遛狗。故C正确。