When a strain of fruit flies homozygous for light body color is crossed with a strain of fruit files homozygous for dark body color all the offspring have light body color. this illustrates mendel's principle of?

I believe this illustrates Mendel's principle of Dominance. In Dominance an organism with a dominant allele for a particular form of a trait will always exhibit that form of the trait, for example Bb; the big B for the dominant trait. Homozygous term is used to refer to an organism that has two identical alleles for a particular trait BB. Heterozygous on the other hand; is a term used to refer to an organism that has two different alleles for the same trait Bb.