被动语态的基本结构是“be + 过去分词”，其中助动词“be”根据不同的时态可以有多种形式。以下是一些关于被动语态的详细用法：
构成：is / am / are + 动词的过去分词
例句：
The library is cleaned every day.
I am asked to study hard.
构成：was / were + 动词的过去分词
例句：
A new shop was built last year.
Dinosaur eggs were laid long long ago.
构成：will be + 动词的过去分词
例句：
A new hospital will be built in our city.
Many more trees will be planted next year.
构成：am / is / are + being + 动词的过去分词
例句：
Uncle Wang is mending my bike now.
They are planting trees over there.
构成：have / has + been + 动词的过去分词
例句：
This book has been translated into many languages.
Many man-made satellites have been sent up into space by many countries.
构成：情态动词 + be + 动词的过去分词
例句：
Young trees must be watered often.
Your homework can be handed in tomorrow.
特殊用法和注意事项：
当不知道或没有必要指出谁是动作的执行者时，常用被动语态。
例句：
The bridge was built last year.
He was elected chairman.
当需要更加强调动作的承受者时，使用被动语态。
例句：
The Great Wall is enjoyed by millions of people all over the world.
The problem is dealt with now.
不及物动词如“happen”, “break down”, “come out”等没有被动语态。
例句：
What happened yesterday？
宾语变主语，主语变宾语，谓语变“be done”，时态不变，数格必须随主语变化。
例句：
Bruce writes a letter every week. → A letter is written by Bruce every week.
练习题：
将下列句子改为被动语态：
1. They built the bridge last year.
2. The book was written by her.
3. The kids were played with by their uncle.