Mesophyll consists of:

Options

A. waxes and cutin
B. photosynthetic cells
C. lignified cell walls
D. cork but not bark

Explanation

### Step-by-Step Solution:

1. **Understanding Mesophyll**: Mesophyll is the internal tissue of a leaf, located between the upper and lower epidermis. It plays a crucial role in the process of photosynthesis.

2. **Types of Mesophyll Cells**: Mesophyll consists primarily of two types of parenchyma cells:
- **Palisade Parenchyma**: These are elongated cells located just beneath the upper epidermis. They are rich in chloroplasts, which are essential for photosynthesis.
- **Spongy Parenchyma**: These are irregularly shaped cells located beneath the palisade layer and above the lower epidermis. They also contain chloroplasts and have air spaces that facilitate gas exchange.

3. **Identifying the Correct Option**:
- **Option A (Waxes and cutin)**: Incorrect, as these are not components of mesophyll.
- **Option B (Photosynthetic cells)**: Correct, as mesophyll cells (palisade and spongy parenchyma) are indeed photosynthetic due to the presence of chloroplasts.
- **Option C (Lignified cell wall)**: Incorrect, as mesophyll cells do not have lignified cell walls; lignification is more characteristic of supportive tissues.
- **Option D (Cork but not bark)**: Incorrect, as cork is a protective tissue and not a component of mesophyll.

4. **Conclusion**: The correct answer is **Option B: Photosynthetic cells**.