第1个回答 2013-10-23
被动语态表示主语是动作的承受者，在被动语态的句子中，动作的执行者，一般由介词by引起的短语来表示，如:We often help them. (主动)我们常帮助他们。They are often helped by us.(被动)他们常被我们帮助。 1、被动语态各时态的形式是由助动词be的各时态的形式加及物动词的过去分词构成。 2、被动语态八种时态的用法例句:被动语态常用的八种时态的基本用法和主动语态各时态的 基本用法相同，只是句中的主语不是动作的执行者，而是动作的承受者，如:(1)一般现在时：Now English is taught in all middle schools in our country. (2)一般过去时：The Great hall of the People was built in 1959. (3)一般将来时: When will the work be finished? (4)过去将来时：He told us that the work would be finished the next day. (5)现在进行时： Your tractor is being repaired now.(6)过去进行时：The child was being examined by the doctor when they came in. (7)现在完成时：The work hasn’t been finished yet. (8)过去完成:The new plan had been carried out before the second experiment began. 3、在下列情况下，一般使用被动语态：（1）当不知道动作执行者是谁或没有必要提到动作执行者时，如：Paper was first made in China. （2）当强调或突出动作承受者的作用时，如：The new machine was invented by a 20-year-old young worker. 4、由主动语态转换为被动语态的几种句型：（1）将一个句子由主动语态转换为被动语态时，可按下列步骤进行：①先将主动结构的宾语改为被动结构的主语；②再将主动语态动词改为被动语态动词；③最后在被动语态之后加介词by，并将主动结构的主语放在by之后（经常被省略），构成介词短语；④由主动语态动词改为被动语态动词时，要注意被动语态动词中助动词be的各种形式变化，因为被动语态动词的不同人称和数是由助动词be不同的形式来表示的，如：Trees are planted every spring.（２）如果主动语态动词后又有直接宾语，又有间接宾语，一般是将间接宾语改为被动语态句中的主语，将直接宾语保留在原处。如将直接宾语改为被动语态句中的主语，将间接宾语保留在原处时，一般要在间接宾语前加介词to或 for，如：Grandma told me an interesting story last night.→Ｉwas told an interesting story last night./ An interesting story was told to me last night.