条件状语从句分为真实条件和非真实条件两种.前者表示真实的或可能变成现实的条件，后者表示非真实的或不可能变为现实的条件.真实条件句要用一般时标将来。

　　例：Oil floats if you pour it on water.

　　The sports meet will be put off if it rains tomorrow.

　　If I were you, I would refuse the money.

　　虚拟式的基本形式 (后面我们再详细讲虚拟语气)

　　If we left now, we should arrive in time.

　　If we had left time, we would have dropped by.

　　If you dropped the glass, it would break.

　　The tennis finals will be put off if it ______ tomorrow afternoon. (2005/4)

　　A. rains B. will rain

　　C. were to rain D. was to rain

　　A

　　让步状语从句，关联词：though, although, if, even if, even though, in spite of the fact that等.

　　例：

　　1. Though it was only nine o’clock, there were few people in the street.

　　2.He went out in spite of the fact that he had a bad cold.

　　Exercises

　　1. If you smoke in a non-smoking section people _____.

　　A) have objected B) objected

　　C) must objected D) will object

　　2. A man escaped from the prison last night. It was a long time _____ the guards discovered what had happened.

　　A) before B) until C) since D) when

　　3. Government cannot operate effectively _____ it is free from such interference.

　　A) so long as B) so that

　　C) unless D) because

　　D C C

　　4. Not that John doesn't want to help you, _____it's beyond his power.

　　A) but that B) for that

　　C) and that D) in that

　　5. Man differ from animals ____ they can think and speak.

　　A) in that B) for that

　　C) with that D) at that