1,-Was the key still there___you went to pick up your child?
-Perhaps.But when I got back,it was missing.
A,while B,although C,once D,unless
2,Although others may not agree,personally,I don't think his plan is practical,___easy to carry out.
A,so is it B,so it is C,nor is it D,nor it is
3,Quite a few applicants were turned down,and I was accepted.Only then did I realize____was I who was fortunate.
A,this B,one C,it D,that
请给出解释哟.