Learn English: Elliptical Adverb Clause
(1). 在时间或地点状语从句中，如果从句中的主语和主句的主语相同，而且从句中的动词为be，则把从句中的主语和be一并省略。
Look out for cars when (you are) crossing the street.
穿越街道时注意车辆。
Fill in the blanks with the given phrases.Change the form where (it is) necessary.
用所给的短语填空，必要的地方可以改变其形式。
Avoid structure of this kind where (it is) possible.
只要可能就要避免这种结构。
(2).在条件状语从句中，如果从句中含有“It+be+形容词”结构，将it和be省略。如果从句中的动词为“助动词+-ed分词”则将主语和助动词一并省略。
If (it is) necessary I’ll have the paper copied.
如果必要我可以请人把这篇文章复印一下。
(3). 在让步状语从句中，当从句中的主语和主句中的主语相同，而且从句的动词为be，则将从句中的主语和be一并省略。
Though (they are) reduced in numbers,they are still strong.
虽然人数减少了，但他们仍很强大。
(4). 在方式状语从句中，省略主语和be的某种形式，只保留形容词、介词短语、不定式、现在分词、过去分词等。
Lucy hurriedly left the room as if (she was) angry.
露西急匆匆地走出房去，好像很生气的样子。
(5). 在比较状语从句中的省略。
省略作主语的what。如：
They have got more than (what) is necessary.
当不同的主语进行比较时，一般省略从句中的谓语，省略的谓语与主句的谓语时态相同；当从句中的主语与谓语（be动词除外）和主句中的主语与谓语相同时，通常省略从句中的主语和谓语，只保留比较部分。
He is taller than his brother (is).
I was working more quickly than he (was).
I have as much confidence in you as (I have confidence) in him.
He has lived here longer than I (has lived).
It was not so hot yesterday as (it is) today.
注意如下区别
She loves the movie more than I(她比我喜欢这个电影)
She loves the movie more than me(她喜欢电影胜过喜欢我）
如果状语从句中的主语是it，谓语是be的各种形式，或状语从句是there be句型时，常可把it和be或there be省略。具体省略结构如下：if, unless, when, whenever +形容词。例如：
Some saldiers would ask him about the threequestions whenever possible (=whenever it waspossible).
You'r better not look up new words in thedictionary when you reading unless necessary(=untess it is necessary)
Correct the mistakes in the follwing sentencesif any (=if there is any)
当从句主语和主句主语不一致时,从句部分要么用完全形式,要么用独立主格结构来表达。例如:
When the meeting was over, all the people went out of the meeting-room.当会议结束时,人们都走出了会议室。(=The meeting over, all the people went out of the meeting-room.)
Look out for cars when (you are) crossing the street.
穿越街道时注意车辆。
Fill in the blanks with the given phrases.Change the form where (it is) necessary.
用所给的短语填空，必要的地方可以改变其形式。
Avoid structure of this kind where (it is) possible.
只要可能就要避免这种结构。
(2).在条件状语从句中，如果从句中含有“It+be+形容词”结构，将it和be省略。如果从句中的动词为“助动词+-ed分词”则将主语和助动词一并省略。
If (it is) necessary I’ll have the paper copied.
如果必要我可以请人把这篇文章复印一下。
(3). 在让步状语从句中，当从句中的主语和主句中的主语相同，而且从句的动词为be，则将从句中的主语和be一并省略。
Though (they are) reduced in numbers,they are still strong.
虽然人数减少了，但他们仍很强大。
(4). 在方式状语从句中，省略主语和be的某种形式，只保留形容词、介词短语、不定式、现在分词、过去分词等。
Lucy hurriedly left the room as if (she was) angry.
露西急匆匆地走出房去，好像很生气的样子。
(5). 在比较状语从句中的省略。
省略作主语的what。如：
They have got more than (what) is necessary.
当不同的主语进行比较时，一般省略从句中的谓语，省略的谓语与主句的谓语时态相同；当从句中的主语与谓语（be动词除外）和主句中的主语与谓语相同时，通常省略从句中的主语和谓语，只保留比较部分。
He is taller than his brother (is).
I was working more quickly than he (was).
I have as much confidence in you as (I have confidence) in him.
He has lived here longer than I (has lived).
It was not so hot yesterday as (it is) today.
注意如下区别
She loves the movie more than I(她比我喜欢这个电影)
She loves the movie more than me(她喜欢电影胜过喜欢我）
如果状语从句中的主语是it，谓语是be的各种形式，或状语从句是there be句型时，常可把it和be或there be省略。具体省略结构如下：if, unless, when, whenever +形容词。例如：
Some saldiers would ask him about the threequestions whenever possible (=whenever it waspossible).
You'r better not look up new words in thedictionary when you reading unless necessary(=untess it is necessary)
Correct the mistakes in the follwing sentencesif any (=if there is any)
当从句主语和主句主语不一致时,从句部分要么用完全形式,要么用独立主格结构来表达。例如:
When the meeting was over, all the people went out of the meeting-room.当会议结束时,人们都走出了会议室。(=The meeting over, all the people went out of the meeting-room.)
