Which of the following is regarded as best contrivances for self pollination?

Options

A. Homogamy
B. Cleistogamy
C. Pollen prepotency
D. Dicliny

Answer

To determine which of the following options is regarded as the best contrivance for self-pollination, we will analyze each option provided:

1. **Homogamy**: This term refers to the condition where the anther and stigma of a bisexual flower mature at the same time. While this does facilitate self-pollination, it does not guarantee it, as there is still a possibility of cross-pollination occurring. Therefore, while homogamy can contribute to self-pollination, it is not the best contrivance.

2. **Clistogamy**: This term describes a condition where the flowers of certain plants never open, which means that the pollen is transferred from the anther to the stigma within the same flower without the possibility of cross-pollination. This makes clistogamy a highly effective mechanism for ensuring self-pollination. An example of a plant exhibiting clistogamy is *Commelina*, and other examples include *Oxalis*. Hence, clistogamy is regarded as the best contrivance for self-pollination.

3. **Pollen Preprotein C**: This refers to a situation where the anthers of different flowers mature first, promoting cross-pollination rather than self-pollination. Therefore, this option does not support self-pollination and is not a suitable answer.

4. **Diclini**: This term refers to unisexuality in plants, where flowers are either male or female. This condition can lead to cross-pollination, especially in monoecious or dioecious plants. Thus, this option does not facilitate self-pollination effectively.

After evaluating all the options, the best contrivance for self-pollination is **Clistogamy**.

### Final Answer:
The best contrivance for self-pollination is **Clistogamy**.