Assuming that both parent plants in the diagram below are homozygous, why would all of the f1 generation have yellow phenotypes?

In the diagram below, what accounts for the green pea seed in the f2 generation?

In a particular plant, leaf color is controlled by gene D. Plants with the dominant allele D have dark green leaves, and plants with the homozygous recessive dd genotype have light green leaves. A true-breeding dark-leaved plant is crossed with a light-leaved one, and the F1 offspring is allowed to self-pollinate. The predicted outcome of this cross is diagrammed in the Punnett square shown below, where 1, 2, 3, and 4 represent the genotypes corresponding to each box within the square. Which of the boxes marked 1-4 correspond to plants with dark leaves?

Which of the boxes correspond to plants with a heterozygous genotype?

The following genotypes were found in a male cat(BbSS) and a female cat(bbSs). Which one of the following choices is true of the phenotype of offspring from these parents?