Clive Papers Inc. (CPI), a printing company, implemented the following controls over its procurement and inventory process. Which of these controls represents a preventive control?

a. The warehouse manager performs an inventory count at the end of each month to identify any damaged or stolen goods.

b. The VP Operations reviews the purchasing report on a weekly basis to identify any unusual activity.

c. A reconciliation of the inventory level, units purchased, and units sold is performed by the assistant controller on a monthly basis.

d. Access to the purchasing module of the information system is restricted to three purchasing agents who are entitled to make purchases for CPI.