用所給的介詞填空
介詞：in,on,at,of ,to ,for
1.This is the classroom which he studied more than ten years ago.
2.The famous player can play two chess games one time.
3.He and his twin brother have a lot common.
4.I'll come condition that my sister is invite,too
5.He arrived at the airport 6:30,just in time to catch his plane.
6.You should go out playing instead working indoors.
7.We are particularly grateful to you your timely help.
8.The president of this college will pay an official visit China in May.
9.He has formed the habit saving money and has set aside a sum.
10.He is so interested his game as to forget everything else.