Stroma is ground substance of

Options

A. Nucleus
B. Chloroplast
C. Mitochondria
D. Endoplasmic reticulum

Answer

### Step-by-Step Solution:

1. **Understanding the Question**:
- The question asks about the ground substance known as "stroma" and which organelle it is associated with.

2. **Identifying the Options**:
- The options provided are:
- Nucleus
- Chloroplast
- Mitochondria
- Endoplasmic Reticulum

3. **Analyzing Each Option**:
- **Nucleus**: The nucleus is the control center of the cell and contains genetic material. It does not have a structure referred to as stroma.
- **Chloroplast**: Chloroplasts are organelles found in plant cells that are responsible for photosynthesis. They contain a viscous fluid known as stroma.
- **Mitochondria**: Mitochondria are the powerhouses of the cell, generating energy through cellular respiration. They do not contain stroma.
- **Endoplasmic Reticulum**: The endoplasmic reticulum is involved in protein and lipid synthesis but does not have a structure called stroma.

4. **Conclusion**:
- Based on the analysis, stroma is specifically associated with chloroplasts, where it serves as the ground substance that contains enzymes for the Calvin cycle, which is part of photosynthesis.

5. **Final Answer**:
- The correct answer is **Chloroplast**.