When a tall homozygous plant was crossed with a short homozygous plant, the f1 offspring were all tall. no short plants were present in the f1 generation.

which principle does this situation represent?

a. the principle of unit characters
b. the principle of dominance
c. the principle of segregation

The answer to the question B which is the principle of dominance. Say the genotype of plant 1 is TT(tall, homozygous) and plant 2 is tt(short, homozygous). T is dominant over t. Crossing the two plants, we end with genotypes that all show Tt. Since T is dominant it will show between the two, resulting in all tall plants.

The  correct answer should be a waste