情态动词的被动语态结构为：情态动词+be+过去分词。
其时态及句型的变化仅由情态动词完成，“be+过去分词”部分不变。 Tables can be made of stone. 桌子可由石头制造。
被动语态的用法：
1. 一般现在时的被动语态构成：is / am / are + 及物动词的过去分词 。
Our classroom is cleaned everyday.
I am asked to study hard.
Knives are used for cutting things.
2. 一般过去时的被动语态构成：was / were + 及物动词的过去分词 。
A new shop was built last year.
Dinosaur eggs were laid long long ago.
3. 现在完成时的被动语态构成：has / have + been + 及物动词的过去分词 。
This book has been translated into many languages.
Many man-made satellites have been sent up into space by many countries.
4. 一般将来时的被动语态构成：will+ be + 及物动词的过去分词 。
A new hospital will be built in our city.
Many more trees will be planted next year.
5. 含有情态动词的被动语态构成：情态动词+ be + 及物动词的过去分词 。
Young trees must be watered often.
Your mistakes should be corrected right now.
The door may be locked inside.
Your homework can be handed in tomorrow.
情态动词被动语态的结构是：情态动词+be+过去分词。其时态及句型的变化仅由情态动词完成，“be+过去分词”部分不变。含有情态动词的主动语态变为被动语态时，要把主动语态中的宾语变为被动语态中的主语；主动语态中的谓语动词变为“情态动词+助动词be+过去分词”；主动语态中的主语变为介词by的宾语，放在句尾。
英语语法的种类
英语语法有：定语从句、宾语从句、状语从句、同位语从句、主语从句、表语从句六种句子的语法。英语时态的语法有16种：一般现在时、一般进行时、一般过去时、一般将来时、现在进行时、过去进行时、将来进行时等。
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