The correct answer is option 'A' - Microsporangia.

Explanation:
The anther is a key structure in the flower of angiosperms (flowering plants) that is responsible for the production of pollen. It consists of four microsporangia, also known as pollen sacs, located at the corners.

1. Anther Structure:
The anther is a bilobed structure, with each lobe consisting of two microsporangia. These microsporangia are located at the corners of the anther, making a total of four microsporangia in a complete anther.

2. Microsporangia:
Microsporangia are the reproductive structures within the anther that produce pollen grains. Each microsporangium contains numerous pollen mother cells, which undergo meiosis to produce haploid microspores. These microspores then undergo mitosis to form mature pollen grains.

3. Pollen Production:
Within each microsporangium, the process of microsporogenesis occurs. It involves the division of microspore mother cells through meiosis, resulting in the formation of microspores. These microspores develop into pollen grains through subsequent mitotic divisions.

4. Pollen Release:
Once the pollen grains are fully developed, the anther dehisces (opens) to release them. This allows for the dispersal of pollen, which is essential for the process of pollination.

5. Pollination and Fertilization:
Pollen grains are transferred from the anther to the stigma of the same or another flower, a process known as pollination. This enables the pollen tube to grow and deliver the male gametes (sperm cells) to the female reproductive structures (ovules) for fertilization.

In summary, the anther is a four-sided structure in flowering plants that consists of four microsporangia located at the corners. These microsporangia produce pollen grains through the process of microsporogenesis, which are then released for pollination and fertilization to occur.