问两道英语语法题（虚拟语气）
I saw you holding your umbrella on the bus just now,but where is it?You ___ it here.
A.should have left B.must have left
My friend said to me on the bus,‘ It’s quite warm here,you ___ so many clothes.’
A.needn’t take B.needn’t have taken
写出答案并说明原因（最好详细易懂些）,
两题正确答案B和A