状语从句中的省略问题

　　用作状语的从句叫状语从句。状语从句可置于句首、句末或句中，一般来说，状语从句都比较完整。但是，在一些状语从句中存在的省略问题，可以归纳为以下两点：

　　1. when, while, if, as if, although / though, as, until, once, whether, unless, where等引导的从句中，如果其谓语为be，而主语与主句的主语相同时，则从句的主语和be可省略。有时从句的主语为it时，也可省略it或从句中的有关成分。如：

　　①When (I am) in trouble, I always turn to my classmates for help. 遇到麻烦时，我总是找同学帮忙。

　　②If(it is) possible, this machine can be fixed at once.可能的话，这台机器会立即修好。

　　③When(water is) pure, water is a colourless liquid. 水清时，是无色的液体。

　　④When(it is) necessary, you can help us to do something.必要时，你可以帮我们做点儿事。

　　2. than, as, no matter what /who等后面成分的省略。如：

　　①We do not use more materials than (it is) necessary.我们不用过多的材料。

　　②We go by way of Beijing as (it was) originally planned.我们按原计划途经北京。

　　③He is much better today than (he was) when I wrote to you last year. 他今天比我去年给你写信时好多

　　1. —Did Jack come back early last night?

　　—Yes. It was not yet eight o’clock _______ he arrived home.

　　A. before B. when

　　C. that D. until

　　2. You should make it a rule to leave things _______ you can find them again. [NMET 1999]

　　A. that B. where

　　C. which D. what

　　3. Give children the space to voice their opinions, ______ they are different from your own.

　　A. until B. even if

　　C. unless D. as though

　　4. I always take something to read when I go to the doctor’s _____ I have to wait.

　　A. in case B. so that

　　C. in that D. as if

　　5. The old tower must be saved, ________ the cost.

　　A. however B. whatever

　　C. whichever D. wherever

　　6. It would be worth trying ______ you can not succeed at once.

　　A. unless B. whether

　　C. as though D. even though

　　7. This set of furniture can last for several generations ______ properly protected.

　　A. that B. although

　　C. if D. and

　　8. Unlike watching TV, reading is a highly active process ______ it requires attention as well as memory and imagination.

　　A. until B. but

　　C. unless D. for

　　Key: 1-4 BBBA 5-8 BDCD