Which one of the following is an example of a weak internal control activity?

	A.	The clerk placing purchase orders also pays vendors.
	B.	One bookkeeper processes the day's cash receipts, and another posts the receipts to the accounts receivable records.
	C.	Access to the room housing the company's central servers is limited to authorized employees. Those employees can enter the room only by using an authorized personal code.
	D.	Before a large invoice amount is paid, the invoice is compared to the purchase order, and the payment is authorized by the responsible manager.