Here's why:

* Homozygous: Means the plant has two identical alleles (versions of a gene) for the trait.

* Dominant: Means the "tall" allele is dominant over the "short" allele. This means that if a plant has even one "tall" allele, it will be tall.

So, a plant with two "tall" genes has two dominant alleles and is therefore homozygous dominant.