How does the structure of the stigma aid in pollination ?

First we need to know what us the function of stigma.
Stigma is the female part of a flower and its job is to catch the pollen grains pollinated from the anther either by wind or insects in order to be fertilized to reproduce.
One feature that stigma has that can help pollination is that they're sticky. That way, the pollen grains can be caught easily when insects brush through them, or catch them by the wind.

The  correct answer should be a waste