I dont't know whom this backpack belong to 还是 belongs to

I dont't know whom this backpack belong to 还是 belongs to I think it ___Tom belong to还是belongs to i dont know who the watch belongs to I am not sure who that book belongs to还是I am not sure whom t is belong to 还是 belongs to belong to的复数是belongs to还是belong tos This book belongs to whom/who? Do you know who this dictionary belongs to?为什么用who,不用whom sth belong to sb 还是 sth belongs to sb? This dress belongs to my sister.为什么是belong+s 想知道是who does this book belong to?还是whom does this book belon This farm( )his aunt.A.is belong to B.belongs C.belongs to D