A horticulturist wants to produce geraniums with specific characteristics. She knows that the trait of red flowers is governed by the allele R (RR and Rr) and the trait of white flowers is governed by the allele r (rr). What do the letters in each box of a Punnett square indicate?

A) the possible combinations of alleles in offspring based on the parents' genetic makeup
B) how to assemble a genetic map of the chromosome on which the alleles are located
C) that both parents show characteristics of the dominant trait
D) the full pedigree of the geraniums