1 as we know, as we know it, as do we know it等的辨析
The plane _____ today was invented in America by Wright Brothers.
A. as we know
B. as we know it
C. as is known by us
D. as do we know it
最佳答案 2017-06-23 12:38
The plane _____ today was invented in America by Wright Brothers.
A. as we know
B. as we know it
C. as is known by us
D. as do we know it
解答：
以上四个选项中，C和D为形式错误。C中的as is known by us应为as is known to us，意义等于as we know。D项中的do属于多余，应删去。
A和B在形式上都正确，但意义和用法不同。A项的as we know是大家都很熟悉的非限制性定语从句，as的先行项为主句内容，as在从句中作主语、宾语、表语，意为“正如……”。as从句可以位于句末、句首和句中，位于句中位置时，通常需要前后用逗号和主句隔开。
本句中 plane 和 today 之间没有逗号，可以排除A项。
因此B项是正确选项。但 as we know it 是什么意思呢？是什么用法？我举出两个词典的解释和例句。
《美国韦氏词典》
As we know it: as it exists now.
The building as we know it is quite different from how it looked when it was first built.
我们现在看到的这座建筑与当初刚建成的时候样子完全不同了。
《麦克米伦英语词典》
As we know it : used when you are talking about something that people are familiar with, especially something that is likely to change
This could mean the end of life as we know it.
这可能意味着我们所熟悉的这种生命的终结。
从以上两部词典的解释和例句我们可以知道as we know it用于一个名词之后，该名词表示人们所熟悉的一个事物，尤其是可能发生变化的事物，as we know it 用来说明该名词指我们现在所了解和熟悉的存在形式。如以前的飞机多为螺旋桨发动机，速度慢，航程短，而现在的飞机多为喷气式、速度快，航程远。因此 the plane as we know it 指我们现在所熟悉的飞机。
这个从句在结构上是状语从句的结构，但起的作用却是对名词的补充性说明。有人解释这种从句是方式状语从句，这种解释是讲不通的，因为这个从句并没有解释谓语动词的方式。如果称其为定语从句，却和定语从句的结构不符，因为定语从句都是由关系代词或关系副词引导的，而as在这里既不是关系代词也不是关系副词，而且从句的it就是指代该名词的人称代词，因此定语从句可以排除。
我认为这个从句是补充性状语从句，as 仍然保留“正如、就像”这样的比较意义。由于不是对全句做补充，而只是补充说明名词的含义，所以放在名词之后。通常不用逗号。
更多的例句：
..., the world as we know it today would have been a completely different place.（北师大版高中英语选修7 Unit20 Lesson3）
Magazines as we know them today began publication around 1882. 我们今天所说的杂志大约在1882年开始出版发行。
Life as we know it needs water and oxygen. 我们所了解的生命需要水和氧气。
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其它 3 个回答
此题选A或B。as we know today 是非限制性定语从句，建议在前后加逗号停顿：The plane, as we know today, was invented in America by Wright Brothers.
C. as is known by us （误）
“为某人所知”，介词用to，改为：as is known to us（= as we know）
D. as do we know it（误）
这也是一个方式状语从句，它是as we know it 的倒装变式，错误跟B 一样。
定语从句as we know 和方式状语从句as we know it/them，含义不同，有细微的差别。以下是选自词典的例句，供参考和比较。
1. He planned to end the welfare system as we know it.
他计划终止现行的福利制度。
来自柯林斯例句
——as we know it 中，it 指代 the welfare system，“我们目前所熟悉的福利制度”。译文中用了“现行的”代替。
2. Let's have your gut reaction to the facts as we know them.
请告诉我们你对我们所了解的这些事实的本能反应。
来自柯林斯例句
——as we know them 中，them 指代the facts， 意为“我们所了解的这些事实”。
3. Industrial policy would mark the end of the free-enterprise system as we know it.
工业政策会促使我们所熟知的自由企业制度寿终正寝。
来自辞典例句
——as we know it 中，it 指代the free-enterprise system，意为“我们所熟知的自由企业制度”。
4. Reform, as we know, is the enemy of revolution.
正如我们所知，改革是革命的大敌。
来自辞典例句
5. As we know, prolixity is a big shortcoming to write articles.
众所周知，罗嗦是写文章的大忌。
来自辞典例句
6. As we know, heat is a form of energy.
正如我们所知道的, 热是能量的一种形式。
来自辞典例句
7. Madame Merle, as we know, had been very discreet hitherto ; she had never criticized.
我们知道, 梅尔夫人一向十分谨慎,从不疾言厉色。
来自辞典例句
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The plane, as we know today, was invented in
A. as we know
B. as we know it
The plane, as we know it, today was invented in
C. as is known by us
D. as do we know it
A答案解析: as we know 定语从句表达的是“正如我们所知”的意思
Life, as we know, needs water and oxygen.
正如我们所知道的那样，生命需要水和氧气。
B答案解析:as we know it
在本句中as引导的是方式状语从句。“as we know it.”是对as前面的名词the plane 的限定，表示”就我们所了解到的the plane言”。也就是说，本句主句所陈述的内容“The plane was invented in America by Wright Brothers.”这一结论只适用于目前人们对飞机是被谁发明的认知，不适用于未来人们对飞机的发明者的认知，由此可见，通过as we know it 对the plane 进行严格限定，陈述内容显得非常严谨.
Life as we know it needs water and oxygen.
就目前我们所认知的生命而言，它是需要水和氧气的。
Life, as we know, needs water and oxygen.
正如我们所知道的那样，生命需要水和氧气。
Magazines as we know them today began publication around 1882.
我们今天所说的杂志大约是在1882年发行的。
Magazines，as we know，today began publication around 1882.
就目前我们所知，杂志大约是在1882年发行的。
There would be no weather, as we know it.
正如我们所知, 也没有天气.
Water is a key ingredient for life as we know it.
就我们所知,水是生命的一个关键元素.
He planned to end the welfare system as we know it.
他计划终止现行的福利制度。
Pessimists tell us that the family as we know it is doomed.
悲观主义者告诉我们说,我们现在的这种家庭注定要崩溃.
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As we know today（状语）, the plane was invented in America by Wright Brothers.
这是符合英语习惯的表达，其它三项多思无益，英语是一项既能，不是科学，应该用碎片时间学习，讲究效率。其它三项的情况在其它题目自然还会遇到，那才会是恰当的例子。
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