十五、复合句——副词性(状语)从句
副词在句中起状语作用，故如果起状语作用的部分为一个句子，那么该句便是副词性从句，也称状语从句。状语从句可细分为：时间、地点、条件、原因、让步、目的、结果、比较、方式等。
状语从句的测试重点为：考查考生对主从句之间逻辑意义关系的把握，看其是否能选择正确的从属连词。
1.条件状语从句的常考知识点
(1)if与unless的用法。
if和unless都是引导条件状语从句的连词，考生应尤其注意unless的用法，因为它表示反面条件，相当于if not“如果不”、“除非”。如：
In debating, one must correct the opponent’s facts, deny the relevance of his proof, or deny that what he presents as proof, if relevant, is sufficient.
(2)复合连词as long as，so long as，as far as，on condition that，in the event that;动词及分词provided(that)，providing(that)，given that, suppose/supposing(that)，assuming，say等引导条件状语从句。如：
You can arrive in Beijing earlier for the meeting provided you don’t mind taking the night train.
Assuming he is diligent in his studies at ordinary times, he is sure to pass the test.
In the event that she has not been informed, I will tell her. (如果……)
You can go swimming on condition that you don’t go too far from the river bank. (如果……)
Suppose it rained, we would still go. (假如……)
Say it were true, what would you do about it? (假如……)
(3)祈使句表示条件。如：Dress warmly, or else you’ll catch cold.
Talk to anyone in the drug industry, and you’ll soon discover that the science of genetics is the biggest thing to hit drug research since penicillin was discovered.
2.让步状语从句的常考知识点
(1)as 引导让步从句，要求用倒装结构，把强调的部分置于句首。如：
Much as he likes her, he does get irritated with her sometimes.
Humble as it may be, there is no place like home.
(2)while引导让步从句。如:
Everybody cheats a little, some psychologists say, while others insist that most people are basically honest and some wouldn’t cheat under any circumstances.
(3)复合连接词for all that和分词granting/granted(that)引导让步从句。如:
Granted you have made much progress, you should not be conceited.
For all that computers can provide us with great help, they shouldn’t be seen as substitutes for fundamental thinking and reasoning skills.
3.时间状语从句的常考知识点
(1)before表示汉语的 “只有/必须……才能”。如:
New ideas sometimes have to wait for years before they are fully accepted.
(2)when引导时间从句时，如果出现在后半句，则表示“这/那时突然”。如：
I have just started back for the house to change my clothes when I heard the voices.
(3)when it comes to 是习惯用法，意为“当谈到……时”。如：
Doing your homework is a sure way to improve your test scores, and this is especially true when it comes to classroom tests.
(4)名词短语、介词短语each /every time, the moment/second/minute, in the time, by the time起连词作用。如:
I hope her health will have improved greatly by the time we come back next year.
My pain must have been apparent the moment I walked into the room, for the first man I met asked sympathetically: “Are you feeling all right?”
Mercury’s velocity is so much greater than the Earth’s that it completes more than four revolutions around the Sun in the time it takes the Earth to complete one.
(5)副词directly, immediately, instantly, now引导时间从句, 相当于as soon as。如:
The policemen went into action directly they heard the alarm.
