为什么这里不要还原to?I heard the boy singing just now.The boy was heard singing just now.

为什么这里不要还原to?I heard the boy singing just now.The boy was heard singing just now. i had to speak loud to make myself heard.这里的heard 是怎么回事 Tom was heard to gou out just now.为什么这里要用was heard I heard Bob was coming back from his journey to France?这句话是对的吗?这里为什么会是was coming? recently polly was( )(hear or heard to try.这里答案是heard,但为什么一个句子里有两个过去式? I'm very furstrated when I heard that I had failed the exam.为什么这里用 furstrated 刚拼错单词了~I'm very frustrated when I heard that I had failed the exam.为什么这里用 frustrated 关于I am sorry to hear that不是说不定式如果发生在谓语动词之前,是要用完成时have done的吗?那这里为什么不说I am sorry to have heard that呢? I wonder why Jenny hasn't written us recently.We should have heard from her by now.为什么这里不用hasn't written to us?write to sb.短语的to 可以省略? I don't know whether you happen to have heard,but I'm going to study in the USA this September.我一直在纠结一个问题 为什么这里要说you happen to have heard 而不是 you have happened to hear? ---from her for a long time i decided to writeto her again having heard 为什么不能用having not heard I heard a car door to open and close为什么有to 请说细一些 I live near an airport and passing planes can be heard night and day.这里为什么用heard 不是应该用一般时态吗 hear .First I heard the breeze in the grass,then in the trees.At first it appeared to be nothing more than just a few trees.I thought I was nowhere.Then he had me close my eyes.FirstI heard the breeze in the grass,then in the trees.这里的grass为什么 I ( ) but ( ) nothing.A.heard,heard B.listened to,heard C.listened,heard D.listened,listened to正确答案是C,我选B错在哪里了?为什么选C?请迅速回答我的问题, 有没有be heard doing的说法看一个例句：he is heard to sing now./he was heard to sing just now 这里为什么用sing,我想都是短暂的动作不应该用singsing吗? I HEARD THAT YOU'RE GETTING MARRIED请问这里 GET 后面为什么加TING啊?这是什么语法啊 I have heard hin speak about you often heard有一种用法,这里不能用speaking么 WalkingI have heard hin speak about you often这里为什么不能用speakingWalking along the river,we heard someone shouting for help.这里为什么又能 I heard him singing there改被动句是heard singing还是heard to sing