1.that ； 在这题也可省略
2.which
3.which that 都可以那还有几题：I have lost the pen__my mother gave me yesterdayThe girl__came to our class this morning comes from Shanghai I think this is the bag__you lost yesterdayIs that the person__you met at the meeting yesterday?Iprefer not to eat too much food__is fried，like French feiesWe study in a room __windows are big谢谢喽！！必定答谢，呵呵that; who; that; 一般不填或者填that ;which ; whose