“___"所需词从这几个中找：in,at,to,of,for,on
1.Have you got used ___sharing the room with other students?
2.He's been looking forward ___ visiting Paris for a long time.
3.They explained that they had never thought___doing anything to offend us.
请写出空中所填介词,并且麻烦告诉我一下每句话用到了什么词组或者语法,所以才填这个介词.