用所给介词填空（答案要告诉我为什么这样做）

题目

用所给介词填空（答案要告诉我为什么这样做）
                                by   in   at   on   with   to   under   for

They like swimming_______the sea.

I wrote a letter________my friend in Australia.

Tom's birthdayis_______Jamuary.

The National Day is_______Friday.

He read the book_______himself.

Last Sunday morning,I played basketball_______my friend Tim.

It is rainy today.My sister is unhappy.I sing a song_____her.

Do you often go to school_______bus or_______foot?

They are singing and dancing______the trees.

Bill is staying________home because he is hill.

答案