You should have put the milk into the ice box, I expect it

You should have put the milk into the ice box, I expect it ____undrinkable by now.

became

had become

has become

becomes

答案及解析：本题考查时间状语从句C选项，句意：你本该把牛奶放到冰里，我想现在这牛奶不能喝了。从句意分析，牛奶已经变质，不能喝了，属过去发生的动作对现在造成影响，再加上by now是现在完成时的典型时间状语，故选C项。A选项，为一般过去时，与题意不符，故排除。B选项，为过去完成时，故排除。D选项，为一般现在时，与题干不符，故排除。故正确答案为C 项。