Final answer:
When self-pollination occurs in the F1 generation, 25% of the offspring will be short and 75% will be tall.
Step-by-step explanation:
When the F1 generation (Tt) is allowed to self-pollinate, each parent will give one factor (T or t) to the F2 generation. So the F2 offspring will have four possible combinations of factors: TT, Tt, tT, or tt.
According to the laws of probability, 25% of the offspring would be tt, so they would appear short. And 75% would have at least one T factor and would be tall.