List the following structures in order from smallest to largest: 1. muscle fiber, 2. myofilament, 3. myofibril, 4. muscle fasciculus

The correct order from smallest to largest is:

1. Myofilament
2. Myofibril
3. Muscle fiber
4. Muscle fasciculus

Explanation:

• Myofilament: These are the smallest structures, consisting of actin and myosin filaments.
• Myofibril: Myofibrils are made up of many myofilaments and are responsible for muscle contraction.
• Muscle fiber: A muscle fiber is a single muscle cell that contains many myofibrils.
• Muscle fasciculus: This is the largest structure, consisting of a bundle of muscle fibers.

Therefore, the correct answer is d. 2 3 1 4.