[求助]GWD中同一题不同答案！

GWD中好像有几道题重复出现可给出的答案居然不同，下面这道请高手帮忙肯定一下：

Q14:

Not one of the potential investors is expected to make an offer to buy First Interstate Bank until a merger agreement is signed that includes a provision for penalties if the deal were not to be concluded.

1. is expected to make an offer to buy First Interstate Bank until a merger agreement is signed that includes a provision for penalties if the deal were
2. is expected to make an offer for buying First Interstate Bank until they sign a merger agreement including a provision for penalties if the deal was
3. is expected to make an offer to buy First Interstate Bank until a merger agreement be signed by them with a provision for penalties if the deal were
4. are expected to make an offer for buying First Interstate Bank until it signs a merger agreement with a provision for penalties included if the deal was
5. are expected to be making an offer to buy First Interstate Bank until they sign a merger agreement including a provision for penalties if the deal were

第2套中给答案是C，第6套给的是A，谁给个确定的答案，谢谢！

I prefer A

因为c选them 无合理指代

这个题目我觉得有问题,如果非要选一个我选择 C

C) is expected to make an offer to buy First Interstate Bank until a merger agreement be signed by them with a provision for penalties if the deal were

但是C选项中the deal 后面跟were我实在不明白怎么能用复数动词

them指代的应该是investors

其实我倒想问一下

为什么系动词用的是复数，LS两位能说一下吗

A里面if后面是虚拟，前面可以不用虚拟么？