my classrom is ?the first floor 答案是on还是at

my classrom is ?the first floor 答案是on还是at at the first floor还是on the first floor “住在第一层”是live on the first floor还是live on first floor "是用on the first floor 因为floor是名词 那at呢 "是用on the first floor 因为floor是名词 那at呢? The canteen is on the first floor. The supermarket is on the first floor. the,on,is,the,canteen,first,floor What is on the floor?的回答是That is my key.还是there is my key. at the second floor 还是on the second floor 4.The music room is on the first floor.(对on the first floor提 Is your classroom on（）floor?one first the first