For the following internal control, please 1) identify the type of control activity/activities, 2) list one relevant audit objective, and 3) suggest a test of control procedure that checks the effectiveness of this control. The test of control procedures listed need to provide reliable audit evidence.

a. Vendors invoices that have been processed for payment are properly cancelled.

b. The receiving reports are pre-numbered and their sequence is accounted for each week.

c. Purchase requisition forms need to be approved by the warehouse supervisor.

d. The payroll accountant does not have access to employees human resource files, which are password protected.