题目内容：

按要求完成下列各题

1.Every year it receives over 750，000 visitors. (改为同义句)

It receives ________ ________ 750，000 visitors every year.

2.The beautiful sweater on the bed is his sister's. (改为同义句)

The beautiful sweater on the bed  ________  ________ his sister.

3.Charlie is so young that he can't take the underground alone. (改为简单句)

Charlie is ________ ________ to take the underground alone.

4.Mrs. Black often stops her son playing computer games. (改为同义句)

Mrs.  Black often  ________ her son  ________  ________ computer games.

5.Someone is knocking at my door.  It must be Tom. (合并为一句)

It ________ be Tom ________ at my door.