考点四、引导名词性从句的从属连词that/whether/if

　　例8.The traditional view is ______ we sleep because our brain is “programmed” to make us do so.
　　A. when
　　B. why
　　C. whether
　　D. that
　　例9.We haven’t settled the question of _____ it is necessary for him to study abroad.
　　A. if
　　B. where
　　C. whether
　　D. that
　　[解析]D、C，引导名词性从句的从属连词that与whether的区别是:句子成分完整且表意确定时选用that连接,句意不确定时选用whether/if连接;借助it,将真正主语或宾语后置,构成“It…that”句型,但whether/if不可;下列情形用whether不用if:与or not 连用,中间无其他词隔开;作介词宾语;在主语从句?表语从句和同位语从句中。

　　考点五、表示比较的从属连词what/as

　　例10. Engines are to machines ______ hearts are to animals.
　　A. as
　　B. that
　　C. what
　　D. which
　　例11._____ I explained on the phone, your request will be considered at the next meeting.
　　A. When
　　B. After
　　C. As
　　D. Since
　　例12.What a table! I’ve never seen such a thing before. It is ________ it is long.
　　A. half not as wide as
　　B. wide not as half as
　　C. not half as wide as
　　D. as wide as not half
　　[解析]C、C、C。what用作从属连词,表比较,用于A is to B what C is to D结构中;而as表示原级比较,常用于as...as结构中,程度修饰语应置于第一个as之前,嵌入的形容词或副词使用原级。另外as还表“正如,按照”,引导方式连词。

　　考点六、表示条件的从属连词if /unless/as long as/once

　　例13. ________ I know the money is safe, I shall not worry about it.
　　A. Even thoughB. UnlessC. As long asD. While
　　例14.Small sailboats can easily turn over in the water ____ they are not managed carefully.
　　A. though
　　B. before
　　C. until
　　D. if
　　例15.You will be successful in the interview ____ you have confidence.
　　A. before
　　B. once
　　C. until
　　D. though
　　例16.I won’t call you, _____ something unexpected happens.
　　A. unlessB. whether C. becauseD. while
　　[解析]C、D、B、A。表条件的连词if/unless/as long as/unless在用法上存在一些差异?as long as用法同only if/on condition that,强调某事的发生以另一事件的发生为前提;if为正面条件,可能会产生好的或坏的结果,若某种条件产生坏的结果,此时的if可用as long as替换; unless为反面条件,表示除非,如果不,故在真实条件句中常和if…not换用;once既表时间,又包含条件,译作一旦。

　　考点七、表示让步的从属连词although/when/while

　　例17. We had to wait half an hour _______ we had already booked a table.
　　A. since
　　B. although
　　C. until
　　D. before
　　例18.______I really don’t like art, I find his work impressive.
　　A. As
　　B. Since
　　C. If
　　D. While
　　【解析】B、D。although/when/while均可表示让步,后两者的用法较为特殊，although/though引导让步连词时不与but和yet连用;而while却表示“部分接受,但并非全部”,或用于“强调两种情况，活动等之间的差距”;when也可表示虽然,尽管,同even if,常置于句末。