根据括号内的要求，改写下列句子。

1. My parents should allow me to study with friends.（改为同义句）

    I should _________ _________ to study with friends.

2. They often clean their classroom after school. （改为被动语态）

    Their classroom _________ often _________ by them after school.

3. Li Lei gave Tom a new pen last week. （改为被动语态）

    A new pen __________ Tom last week.

4. It took him ten years to finish writing the book.（改为同义句）

    He _________ ten years __________ the book.

5. They will publish these story-books next month.（改为被动语态）

    These story-books __________ next month.