The chromatin material which takes darker stain in interphase is called:-

Options

A. Euchromatin
B. Heterochromatin
C. Primary constriction
D. Satellite body

Answer

To answer the question, "The chromatin material which takes darker stain in interphase is called:", we need to analyze the options provided and understand the characteristics of different types of chromatin.

### Step-by-Step Solution:

1. **Understanding Chromatin**: Chromatin is a complex of DNA and proteins found in the nucleus of eukaryotic cells. It exists in two forms: euchromatin and heterochromatin.

2. **Types of Chromatin**:
- **Euchromatin**: This is the loosely packed form of chromatin that is actively involved in transcription. It does not take a dark stain during interphase because it is less condensed.
- **Heterochromatin**: This is the tightly packed form of chromatin, which is generally inactive in terms of transcription. It takes a darker stain because of its dense packing.

3. **Analyzing the Options**:
- **Option 1: U-chromatin**: This is not a standard term used in chromatin classification. It is likely a misnomer or confusion with euchromatin, which is not the correct answer.
- **Option 2: Hydrochromatin**: This term is not commonly used in scientific literature. However, if we consider the context, it seems to refer to heterochromatin, which is the correct answer as it takes a darker stain.
- **Option 3: Primary constriction**: This refers to the centromere region of chromosomes, which is not a type of chromatin and does not answer the question.
- **Option 4: Satellite body**: This refers to specific regions of chromosomes that are not related to the staining characteristics of chromatin during interphase.

4. **Conclusion**: The chromatin material that takes a darker stain during interphase is heterochromatin. Therefore, the correct answer is **heterochromatin**.

### Final Answer:
The chromatin material which takes a darker stain in interphase is called **heterochromatin**.