The full explanation in RMC is as below -
The question is written from the sellers perspective, the contract could be wrong or the customer could be wrong but this should have been identified earlier if proper project management is followed. A seller cannot issue a change request(although they can request one). Did you select meeting all the team members? Remember project management is not about making every decisions will all the team members. the best choice is involving the concerned team member and reviewing the requirements. If such a problem has arisen it could mean that something was wrong in WBS dictionary or in how the member completed the work
Therefore a,b and d are not the correct choices
i think the only thing that remains relevant is that since the question is from sellers perspective raising a change request is not an option and thus through process of elimination c is the right choice. However should we use this as a general rule?