The cross of RR and WW will produce 100% RW. All offspring have the genotype RW. All offspring are considered as roan cows (mix of red and white color). This is an example of codominance. Codominance is where the alleles of a gene pair present in the heterozygote are entirely conveyed. The offspring possess phenotype's combination of the parents. It means the trait is neither dominant not recessive.
Incomplete dominance is where one allele for a definite trait is not entirely conveyed by its paired allele. Complete dominance is where the dominant allele entirely concealed the recessive allele's outcome that are seen in heterozygous conditions. Multiple alleles is where the population possess more than two alleles of similar gene.
Answer - Option A - co-dominance