GWD 03-03

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

句首中 not one of the inverstors用单复数都可以，转到句尾：the deal应该用动词单数，所以排除ACE。但是答案是C，为什么？

貌似有虚拟意味

很不明白为什么用虚拟。。

斑竹果然高手！我之前没有想到会用虚拟。

句首的表达单复数都可以用吗？

C中:

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

这里的them应该是指句首的Not one of the potential investors ，所以应该用are对应呀，可是用了is，不符合主谓一致啊，为什么答案是C?

顶,大牛讲讲,为什么用虚拟语气