From a pmp prepcast email:
“The A Guide to the Project Management Body of Knowledge (PMBOK® Guide) mentions six competing project constraints. Namely: Scope, Quality, Schedule, Budget, Resources, and Risk. Your goal as the project manager is to balance the needs of these constraints and deliver your project successfully.”

But in one of the questions of the day:

Yesterday's Answer
> Which of the following are the project constraints?
>
> A.) Scope, Schedule, Budget, Personnel, Quality, Risk
> B.) Scope, Schedule, Budget, Resources, Quality, Risk
> C.) Scope, Schedule, Cost, Resources, Quality, Risk
> D.) Scope, Schedule, Cost, Personnel, Quality, Risk
>
> C.) is correct. The competing project constraints that you as the project manager must balance are Scope, Quality, Schedule, Cost, Resources, and Risk.

Is cost or budget a competing constraint?
Thank you.