天山－7－14,not until是什么时候虚拟来着？

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.
A. 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

B. 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

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

D. 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

E. 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

大案是A当时糊里糊涂的选了C，就是隐约的记着not until怎么怎么用就可以虚拟了。谁记得指点一下啊

THKS

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

为什么不可以？

因为until, when, after可以做conjunction ，这样的话后面是一句话，而且没不用虚拟。只有一些抽象名词(requirement)后面才用虚拟

C: them without reference,should use single.

verb 'were' to explain this is not a materalize fact.