1.中文：他们结婚两年了。
They have married for two years.
They have been married for two years.(表示已婚状态的持续，要用完成时的被动式。)
2.中文：他被所有学生嘲笑。
He was laughed by all the pupils.
He was laughed at by all the pupils.(不及物动词+介词=及物动词，变被动语态时介词不能省略。)
3.中文：英语难学。
English is difficult to be learned.
English is difficult to learn.(英语难学=学英语难，也可说Its difficult to learn English。原句的'主语实际上是不定式的逻辑宾语，不定式要用主动形式。)
4.中文：汤姆问我这些岛屿是否属于美国。
Tom asked me if these islands are belonged to America.
Tom asked me if these islands belonged to America.
5.中文：中国发生了很大变化。
Great changes have been taken place in China.
Great changes have taken place in China.
6.中文：战争于一九三七年爆发。
The war was broken out in 1937.
The war broke out in 1937.(take place，break out，happen，belong to等不及物动词或短语动词没有被动语态形式。)
7.中文：我看不清黑板。也许你需要检查你的眼睛。
