In grasses what happens in microspore mother cell for the formation of mature pollen grains?

The correct option is B One meiotic and one mitotic divisions
The grass is a monocot plant. Primary sporogenous cell gives rise to microspore mother cells or pollen mother cells. Each MMC on reduction division gives rise to 4 microspores or pollens is called microsporogenesis. Karyokinesis is of successive type. The successive type of cytokinesis is common in monocots. Here both meiotic I and II nuclear divisions are followed by wall formation and it leads to isobilateral tetrad.

So the correct answer is "One meiotic and one mitotic division".