Select the mismatched pair.

Options

A. Storage of pollen grains `-196^(@)C`
B. Pollen allergy - Carrot grass
C. Chasmogamous flowers - Exposed anthers and stigmas
D. Xenogamy - Self pollination

Explanation

To solve the question of selecting the mismatched pair, we will analyze each of the given options step by step.

### Step-by-Step Solution:

1. **Analyze Option 1: Storage of pollen grains at -196 degrees Celsius.**
- This statement is correct. Pollen grains can be stored at very low temperatures, such as -196 degrees Celsius, which is the temperature of liquid nitrogen. This helps in preserving their viability for future use.

2. **Analyze Option 2: Pollen allergy by the carrot grass.**
- This statement is also correct. Carrot grass (often referred to as Bermuda grass) is known to cause pollen allergies in many individuals when its pollen is inhaled.

3. **Analyze Option 3: Chiasmogamous flowers have exposed anthers and stigma.**
- This statement is correct as well. Chiasmogamous flowers are characterized by their open structure, allowing for the exposure of anthers and stigma, facilitating cross-pollination.

4. **Analyze Option 4: Xenogamy.**
- This statement is incorrect. Xenogamy refers specifically to cross-pollination, where pollen from one flower fertilizes the ovule of another flower of the same species. The term itself is not mismatched, but the context in which it is presented may imply a misunderstanding.

### Conclusion:
The mismatched pair is **Option 4** because it is presented in a way that may confuse the definition of xenogamy with other types of pollination, but it is fundamentally correct in its definition.

### Final Answer:
**Option 4** is the mismatched pair.

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