I think the quest should be" Which of the following should you (the buyer) pay attention to when you close a contract?" because the answer is "Perform regular procurement audits." which is Tools and Techniques for close procurements!! 

Am I right??

Which of the following should you (the buyer) pay attention to when you administer a contract?

                Choice 1  Ensure that contractual obligations are met.

                Choice 2  Apply appropriate project management processes to the contractual relationship and integrate the outputs from these processes to the overall management of the project.

               Choice 3  Monitor payments to the seller.

                Choice 4  Perform regular procurement audits.

                Correct Choice : 4

 Justification :

                A procurement audit is a structured review of the procurement process originating from Plan Procurements process through Administer Procurements process. This is one of the tools and techniques used in Close Procurements process.

 Reference: PMBOK® Guide Fourth Edition, Pages 336 and 343