Cross pollination is

Options

A. Autogamy
B. Allogamy
C. Chasmogamy
D. Cleistogamy.

Answer

**Step-by-Step Solution:**

1. **Understanding Cross Pollination**: Cross pollination refers to the transfer of pollen grains from the anther of one flower to the stigma of another flower. This process is essential for genetic diversity in plants.

2. **Identifying the Correct Term**: The term that specifically describes cross pollination is "allogamy." In allogamy, the pollen comes from a different plant of the same species, ensuring that the genetic material is mixed.

3. **Differentiating from Other Terms**:
- **Autogamy**: This is self-pollination, where pollen is transferred from the anther to the stigma of the same flower or another flower on the same plant.
- **Chasmogamy**: This term refers to flowers that are bisexual and have exposed anthers and stigmas, allowing for both self and cross-pollination to occur.
- **Clistogamy**: In this case, the flowers do not open, and self-pollination occurs because the pollen falls on the stigma of the same flower.

4. **Conclusion**: Based on the definitions and characteristics of each term, the correct answer to the question "Cross pollination is" is **allogamy**.