Bye

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

A is the OA.
As far as I know, the correct structure is "if X were to do...., Y should/would do...". However, it doesn't fall into the structure I mentioned.
Is there a grammar rule that I miss?
Thanks in advance.
这个题有争议啊。。。。我也选了A，国外坛子上还有人说OA是A呢。。。。到底是C还是A呀