Raphides are needle-like crystals made up of

Options

A. Calcium carbonate
B. Calcium sulphate
C. Calcium oxalate
D. Calcium pectate

Explanation

### Step-by-Step Solution:

1. **Understanding Raphides**: Raphides are defined as needle-like crystals found in certain plants. They are known for their sharp structure.

2. **Identifying the Composition**: The question asks what these needle-like crystals are made of. The options provided include calcium carbonate, calcium sulphate, calcium oxalate, and calcium pectate.

3. **Analyzing the Options**:
- **Calcium Carbonate**: Commonly found in various forms but not typically in needle-like structures.
- **Calcium Sulphate**: Generally forms different types of crystals, not specifically needle-like.
- **Calcium Oxalate**: Known to form raphides, which are indeed needle-like crystals.
- **Calcium Pectate**: Primarily involved in the structure of plant cell walls, not in the formation of needle-like crystals.

4. **Conclusion**: Based on the analysis, raphides are specifically made up of calcium oxalate. They serve a protective function in plants and are typically found in specialized cells known as idioblasts.

5. **Final Answer**: Therefore, the correct answer is that raphides are needle-like crystals made up of **calcium oxalate**.