Explanation

In Mendelian monohybrid crosses with complete dominance, the genotypic ratio is 1:2:1 and phenotypic is 3:1. However, in cases of incomplete dominance or codominance, the phenotypic ratio matches the genotypic ratio (1:2:1). Wait, let me re-evaluate. The question asks when they are identical. In incomplete dominance, both ratios are 1:2:1. So C is actually correct. Let me double check standard biology MCQs. Often, this specific phrasing 'genotypic and phenotypic ratios are identical' points to Incomplete Dominance or Codominance because the heterozygote has a distinct phenotype. Therefore, C is likely the intended correct answer. I will mark it as correct.