从句的主语与主句的主语一致时，从句可以省略主语，从句的谓语动词采用其V-ing结构。例如： Although working very hard, he failed in the final exam. (Although he worked very hard,…) 我能理解的是从句和主句主语相同，且从句有be动词时，从...
You think this letter could come from Tom.
作疑问句时 ,do you think..还是宾语从句吗？ 还是都变成插入语，怎么判断？
Whom do you think this letter could come from?
Do you think this letter could come from Tom?
...用法正确吗。或者：Yesterday, i went to shopping with my mother. When we went out the market, i noticed a man. He standed in the cold air. 这里的 standed，可以改成 was standing吗。关于这两种时态，语法书上说的区别都能弄懂，但是碰到的...
...on the steep sides of a mountain. 句中perched怎么理解： 1. 理解成定语从句的谓语 a tiny village
(which / that) perched on the steep sides of a mountain2. 理解成过去分词，相当于 a tiny village
(which / that ) was perched on the steep sides of a mountain. 我的疑问主要...
...的：Prepositions are not used before a number of common
expressions of time beginning next, last, this, that (sometimes), one, every,
each, some, any (in an informal style), all.以 Swan 提到的 every 为例，在英语原版语法著作中就可以找到反例，如由著名语言学者 Laurie ...
Migrating to cities has become the choice for many people from the countryside."to cities"这里是做状语还是做migrating的补语呢？Exposure to high levels of radiation is harmful to your health.这里的介词短语可以看做是exposure的后置定语吗？