We've been through all this before.
A、We've experienced all this before.
B、We've discussed these things before.
C、We've thought over about these things before.
D、We've forgotten all these things happened before.
【正确答案】：B
【题目解析】：此题关键是理解be through在此处的含义。through在此指“从头到尾，自始至终”，根据上下文，此处指“我们已经将这些事情从头至尾讨论过了”，所以为discuss。答案为B。
