Across between two pure bred homozygous parental strains (one of which is homozygous dominant, the other homozygous recessive) will result in an f1 generation of offspring that are all and express the dominant phenotype.

Heterozygous

Explanation:

A pure breed (homozygous) plant that is dominant will have the following genotypes: AA

A pure breed (homozygous) plant that is recessive will have the following genotypes: aa

When you cross these two plants their offspring will all be heterozygous having the genotypes Aa

But the offspring plants (F1 generation) will all display traits of the dominant plant bacause the traits of the recessive allele (a) is being masked by the dominant allele (A)

the answer is 1. photosynthesis. glad to

that is wrong, its not thymus.