试题：You should have put the milk in the ice-box; I expect it

试题：You should have put the milk in the ice-box; I expect it ____undrinkable by now.
试题：You should have put the milk in the ice-box; I expect it ____undrinkable by now.
A.became
B.has become
C.had become
D.becomes
为什么这里不能用 became 也是过去式啊(变了) 为什么非要用现在完成时