There are many Christmas cards____but I didn't know which on

There are many Christmas cards____but I didn't know which on There are too many books,i don`t know which还是which one to ch There are so many kinds of bags.I can't decide___.A.which on there were many christmas cards (),but i did not know which There are many presents.I really don't know _____. There are -- many beautiful clothes that we don't know which There are so many beautiful dresses that I hardly know which 单项选择 There are so many books_____ that I don not know which there are so many nice boys,i really dont know which one什么（c l didn't know which one I should choose.改为同义句:I didn't know I didn't know which botton to press I ca nt decide which one to buy ,because there are so many t