If a corn plant has a genotype sstt, what are the possible genetic combinations that could be present in a single grain of pollen produced by the plant?

Sstt. SStt and sstt

For this, you need to draw a Punnett square and cross two parents' Ss tt.

St and st on each parent's place and cross them (photo).

You'll have an offspring 25% SStt, 50% Sstt, and 25% sstt.

If you say that capital S is dominant characteristic over lowercase s, you'll have 75% chances of the offspring showing it and only 25% of the offspring showing the recessive one.

the endomembrane system i think