Which of the following pairs of structures is incorrectly matched?

Options

A. Chloroplast-grana
B. Flagella-actin microfilaments
C. Nucleus-chromatin
D. Mitochondria-cristae

Explanation

To determine which pair of structures is incorrectly matched, we will analyze each pair one by one:

1. **Chloroplast and Grana**:
- Grana are stacks of thylakoids found within chloroplasts. Thylakoids are membrane-bound structures where the light-dependent reactions of photosynthesis occur.
- Therefore, this pair is correctly matched.

2. **Flagella and Actin Myofilaments**:
- Flagella are long, whip-like structures that enable movement in many cells. They are primarily made up of a protein called flagellin, not actin.
- Actin myofilaments are part of the cytoskeleton and are involved in muscle contraction and other cellular movements.
- Hence, this pair is incorrectly matched.

3. **Nucleus and Chromatin**:
- Chromatin is a complex of DNA and proteins found in the nucleus of eukaryotic cells. It condenses to form chromosomes during cell division.
- This pair is correctly matched.

4. **Mitochondria and Cristae**:
- Cristae are the folds of the inner membrane of mitochondria. These folds increase the surface area for chemical reactions, particularly those involved in ATP production.
- This pair is also correctly matched.

After analyzing all pairs, the only incorrectly matched pair is **Flagella and Actin Myofilaments**.

### Final Answer:
The incorrectly matched pair is **Flagella and Actin Myofilaments**.