Identify the correct statement .

Options

A. Arrangement of microtubule in centriole is 9+3.
B. The fimbriae are elongated tubular structures made of a special protein.
C. Structure of chromosomes can be best studied at metaphase .
D. Heterochromatin is genetically more active chromatin.

Answer

To solve the question of identifying the correct statement, we will analyze each of the four statements provided.

### Step-by-Step Solution:

1. **Statement 1: Arrangement of microtubule in centriole is 9 plus 2.**
- This statement is incorrect. The arrangement of microtubules in centrioles is actually 9 triplets (not doublets) arranged in a cylindrical shape, hence it is referred to as 9 plus 0. The 9 plus 2 arrangement is characteristic of cilia and flagella, not centrioles.

2. **Statement 2: Fimbria are elongated tubular structures made up of a special protein.**
- This statement is also incorrect. Fimbriae are short, hair-like structures that are primarily involved in adhesion and are not elongated tubular structures. They are not made of a special protein but are composed of pilin protein, and they are much shorter than flagella.

3. **Statement 3: Structure of chromosome can be best studied at metaphase.**
- This statement is correct. During metaphase, chromosomes are highly condensed and aligned at the metaphase plate, making them easily observable under a microscope. This is the stage where the structure of chromosomes can be best studied.

4. **Statement 4: Heterochromatin is genetically more active.**
- This statement is incorrect. Heterochromatin is the densely packed form of DNA and is generally transcriptionally inactive. In contrast, euchromatin is the less condensed form of chromatin that is more active in transcription.

### Conclusion:
Based on the analysis of the statements, the correct answer is **Statement 3: Structure of chromosome can be best studied at metaphase.**