.Though having discussed it for long, they still haven’t reached an agreement__________they sho

.Though having discussed it for long, they still haven’t reached an agreement__________they sho..

C

连词辨析。That因为，以至于；if是否，如果；whether是否，不论；what什么。句意：尽管讨论了很久，他们仍旧没有达成协议，是否他们应该想这个项目投资。If还有如果的含义，用if会引起歧义时，只用whether。如用whether可避免歧义。故选C。