Read the given Statements for skeletal muscles
(i) Thin filaments are firmly attached to the Z - line .
(ii) The light band is also called the I - band and contains mostly actin.
(iii) A sarcomere is the functional unit of a myofibril between two adjacent A - bands .
(iv) The central part of the thick filament , not overlapped by the thin filament is called the H - zone
Which of these is/are CORRECT ?

Options

A. i, ii, iii, iv
B. i, ii, iii
C. i, ii, iv
D. i, ii

Answer

To determine which statements about skeletal muscles are correct, let's analyze each statement step by step:

### Step 1: Analyze Statement (i)
**Statement (i):** Thin filaments are firmly attached to the Z-line.

**Analysis:** This statement is correct. In skeletal muscle, the thin filaments (actin) are indeed anchored to the Z-line, which is a boundary structure of the sarcomere.

### Step 2: Analyze Statement (ii)
**Statement (ii):** The light band is also called the I-band and contains mostly actin.

**Analysis:** This statement is also correct. The light band, known as the I-band, primarily consists of actin filaments.

### Step 3: Analyze Statement (iii)
**Statement (iii):** A sarcomere is the functional unit of a myofibril between two adjacent A-bands.

**Analysis:** This statement is incorrect. A sarcomere is defined as the segment between two Z-lines, not between two A-bands. The A-band refers to the region containing thick filaments (myosin).

### Step 4: Analyze Statement (iv)
**Statement (iv):** The central part of the thick filament, not overlapped by the thin filament, is called the H-zone.

**Analysis:** This statement is correct. The H-zone is indeed the central region of the A-band where there is no overlap with thin filaments.

### Conclusion
Based on the analysis:
- Statement (i) is correct.
- Statement (ii) is correct.
- Statement (iii) is incorrect.
- Statement (iv) is correct.

Thus, the correct statements are (i), (ii), and (iv). The answer is that statements 1, 2, and 4 are correct.

### Final Answer
The correct statements are: 1, 2, and 4.

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