Question

In summer milk will quickly go bad_____ it is put into a fridge.

A．though

B．unless

C．because

D．once

Answer 1

B

试题分析：句意:在夏天，牛奶很快就会变质，除非把它放在冰箱里。though虽然，尽管，引导让步状语从句；unless 除非，如果不，引导条件状语从句；because 因为，引导原因状语从句；once曾经，一旦，一次。根据句意可知选B。