2. A plant which is homozygous short (tt) is crossed with a plant that is homozygous tall (TT). What is the percentage of plants will have a heterozygous genotype?

The genotype for homozygous short is tt, and the genotype for homozygous tall is TT.
If we cross multiply these genotypes, the resulting offsprings would be:
Tt, Tt, Tt, Tt
The percentage of plants that has a heterozygous genotype is 100%