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.
