Final answer:
The internal control procedure being violated by West Texas Clothing Store is the separation of duties.
Step-by-step explanation:
The internal control procedure being violated by West Texas Clothing Store is D) Separation of duties is necessary. Separation of duties refers to the practice of dividing responsibilities among different employees to reduce the risk of fraud or errors. At West Texas Clothing Store, the sales employee is both assisting customers and handling cash, which violates the principle of separation of duties. Ideally, one employee should assist customers while another employee handles the cash and completes the cash-count form.