The correct option is D Non sticky pollens with closed stamen
Maize plants have unisexual flowers that is they either have the male or the female reproductive organ. When the agent of pollination is wind, then the stamen needs to be exposed , so that the pollen grains can easily get transported to the pistil. Pollen grain needs to be non sticky as if they are sticky, most of them would get stuck to different places while the wind is blowing.