Striations in the striated muscles are due to-

The correct option is D Specialized arrangement of myofilaments
The striations are found due to the presence of specialized arrangement of myofilaments. The specialized myofibrils or myofilaments are actin and myosin. Myofilaments are the filaments of myofibrils. These filaments regulate the contraction of muscles.
Sarcomere is the repeating unit of skeletal myofilaments which gives striated appearance to the skeletal muscle.

So, the correct answer is- specialized arrangement of myofilaments.