Final answer:
a. the arrangement of myofilaments. The striations of a skeletal muscle cell are produced by the arrangement of myofilaments of actin and myosin in sarcomeres.
Step-by-step explanation:
The striations of a skeletal muscle cell are produced by the arrangement of myofilaments of actin and myosin in sequential order from one end of the muscle fiber to the other. These myofilaments, along with regulatory proteins such as troponin and tropomyosin, are organized in sarcomeres, which are the smallest contractile portions of a muscle. The alternating dark A bands and light I bands repeat along the myofibrils, creating the striated appearance of the skeletal muscle fiber.