解放军文职考试：as引导

　　as引出非限定性定语从句时，代替整个主句，对其进行说明但通常用于像as we all know, as it is known, as is known to all, as it is, as is said above, as always mentioned above, as is usual, as is often the case, as is reported in the newspaper等句式中。as在非限定性定语从句中作主语、表语或宾语，且引出的从句位置比较灵活，可位于句首或句末，也可置于主句中间。通常均由逗号将其与主句隔开。as有“正如……， 就像……”之意。

　　如：As is known to the United States, Mark Twain is a great American writer.

　　美国人都知道，马克·吐温是一位伟大的美国作家。(as在从句中作主语)

　　He forgot to bring his pen with him, as was often the case.

　　他忘了带笔，这是常事。(as在从句中作主语)

　　He is absorbed in work, as he often was.

　　他正在全神贯注地工作，他过去经常这样。(as在从句中作表语)

　　As we all know, the earth is round.

　　众所周知，地球是圆的。(as在从句中作宾语)

　　The two brothers were satisfied with this decision，as was agreed beforehand.

　　两兄弟对此决定都满意，这项决定在事前都已得到他们的同意。(as在从句中作主语)

　　Taiwan is，as you know，an inseparable part of China.

　　你知道，台湾是中国不可分割的一部分。(as在从句中作宾语)

　　“介词+关系代词”引导非限制性定语从句：在介词后引导非限制性定语从句。

　　难：句意相同

　　as it is known to all (that...) (as 做状语从句连词，是状语从句, 可以加that)

　　与 as is known to all (as做主语，是定语从句)

　　与 it is known to all that... (主语从句，it是形式主语)

　　既：As is widely known, the moon is closer to the us than the sun.(定从)= Thatthe moon is closer to the us than the sun is widely known.(主从)= it is widely known thatthe moon is closer to the us than the sun.(主从)

　　As it is known to everyone, I thought you knew about it too.(状从)[1]

　　关系代词which有时并不代表主句中某一确定的词，而是概括整个主句的意思。介词的选择取决于它与先行词的搭配或与从句中谓语动词的搭配。

　　They were short of sticks to make frames for the climbing vines，without which the yield would be halved.

　　他们缺搭葡萄架的杆儿，没有它们产量会减少一半。

　　They thanked Tom，without whose support they would not have succeeded.

　　他们很感激Tom，没有他的支持他们是不会成功的。