Which one of the following procedures would best detect the theft of valuable items from an inventory that consists of items selling for hundreds or thousands of dollars?

a. Maintain a perpetual inventory master file of only the more valuable items with frequent periodic verification of the validity of the perpetuals.

b. Have an independent CPA firm prepare an internal control report on the effectiveness of the administrative and accounting controls over inventory.

c. Have separate warehouse space for the more valuable items with sequentially numbered tags.

d. Require an authorized officers signature on all requisition for the more valuable items.