The correct answer to this question is C. The hardest part of a project manager's job is managing the constraints. There are six contraints of a project that influence each other: scope, quality, cost, resources, risk, and time.
If resources are not available, the time to deliver will increase, which can usually result in the increase of project cost because alternate resources are usually more costly. If the quality of the project is decreasing, more resources may be required, which will increase the cost, as well as the time to deliver.
If scope creep occurs on the project, the time, cost, and resources will increase, and the quality will most likely decrease, causing an increased risk on the delivery.