Speculation, that is C, is your anwer. The idiomatic expression "to be rampant" means that something unwelcome spreads unchecked.
The abstract noun "speculation", according to Collins's dictionary, means the act or instance of speculation or a supposition or theory arrived at through speculation. In this case, people were worried about the company closing or not. They did not know for certain what would happen, so perhaps they speculated what to do afterwards.