Sclereids are spherical, oval or cylindrical, highly thickened dead cells. These are made up of
a) Parenchyma
b) Collenchyma
c) Sclerenchyma
d) Aerenchyma

Options

A. Parenchyma
B. Collenchyma
C. Sclerenchyma
D. Aerenchyma

Answer

To answer the question regarding the composition of sclereids, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Definition of Sclereids**: Sclereids are specialized cells that are characterized by their shape (spherical, oval, or cylindrical) and their thickened cell walls. They are also dead cells, meaning they do not contain living protoplasm.

2. **Analyze the Options**:
- **a) Parenchyma**: These are living cells with thin walls and contain protoplasm and vacuoles. Therefore, this option can be excluded as sclereids are dead cells.
- **b) Collenchyma**: These are also living cells, characterized by their elongated shape and medium thickness of cell walls. Like parenchyma, they contain protoplasm and cannot be the answer.
- **c) Sclerenchyma**: This type of tissue consists of dead cells with thick walls and no protoplasm. This matches the description of sclereids perfectly.
- **d) Aerenchyma**: This tissue contains air-filled spaces and is also made up of living cells. It can be excluded as it does not match the characteristics of sclereids.

3. **Conclusion**: After analyzing all the options, the only type of tissue that fits the description of sclereids (spherical, oval, or cylindrical, highly thickened dead cells) is **sclerenchyma**.

### Final Answer:
**c) Sclerenchyma**

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