Read the following statements and select the correct option :
I. In the skeletal muscles fibre, large number of myofilaments are arranged in the sarcoplasmic .
II. The central part of an anisotropic band where the only thick , filament is present and thin filament is absent is called 'A' band.
III. In the resting state , a tropomyosin protein masks the active b binding sites for myosin on the active filaments .
IV. The junction between a motor neuron and the sarcolemma of the muscle fibres is called motor-end plate.

Options

A. I , II and IV are true
B. II, III and IV are true
C. I and IV are true
D. only IV true

Answer

To solve the question, we need to evaluate each of the given statements about skeletal muscle fibers and select the correct option based on their accuracy.

### Step-by-Step Solution:

1. **Evaluate Statement I**:
- "In the skeletal muscle fiber, a large number of myofilaments are arranged in the sarcoplasmic."
- This statement is **correct**. Myofilaments (actin and myosin) are indeed arranged in the sarcoplasm of skeletal muscle fibers.

2. **Evaluate Statement II**:
- "The central part of an anisotropic band where the only thick filament is present and thin filament is absent is called 'A' band."
- This statement is **incorrect**. The A-band contains both thick (myosin) and thin (actin) filaments. The region where only thick filaments are present is known as the H-zone, which is part of the A-band.

3. **Evaluate Statement III**:
- "In the resting state, a tropomyosin protein masks the active binding sites for myosin on the active filaments."
- This statement is **correct**. Tropomyosin indeed covers the binding sites on actin filaments, preventing myosin from binding during the resting state.

4. **Evaluate Statement IV**:
- "The junction between a motor neuron and the sarcolemma of the muscle fibers is called the motor-end plate."
- This statement is **correct**. The motor-end plate is the specialized region of the sarcolemma at the neuromuscular junction where the motor neuron communicates with the muscle fiber.

### Summary of Statements:
- Statement I: Correct
- Statement II: Incorrect
- Statement III: Correct
- Statement IV: Correct

### Conclusion:
The correct option includes statements I, III, and IV. Therefore, the correct answer is **Option 3** (which includes statements 1, 3, and 4).