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

题目给出的答案是c,但是有点不明白until后面也要用虚拟语气么agreement be signed

我也觉得是a