The genotype RrYy is referring to two genes, one with the alleles R/r and the other with alleles Y/y. The genes are inherited separately, so we can have gametes with different combinations of the alleles, but always with one allele for each gene.
In this case, the possible alleles would be these: RY, Ry, rY, ry.
Want would not be expected is having the two alleles of the same gene in a single gamete, which means C) yy would be the right answer.