In a particular plant, green seed color is dominant to yellow seed color. If a homozygous
green seed plant is crossed with a yellow seed plant, what percent of the offspring would
be heterozygous?

100% will be heterozygous green.

Explanation:

Since both parents (green and yellow) are homozygous and green is dominant, when they are crossed all the resultant offsprings will have both genes of green and yellow in their genotype but will appear as green( phenotype) because the green colour is dominant and has masked the yellow colour which is recessive.