, in a typical monohybrid cross with complete dominance, the F2 phenotypic ratio is 3:1 while the genotypic ratio is 1:2:1. However, in cases of Incomplete Dominance (e.g., Antirrhinum flower colour) and Co-dominance (where F1 resembles both parents), the F1 phenotype is distinct from the homozygous parents. Consequently, the F2 generation exhibits a phenotypic ratio that matches the genotypic ratio of 1:2:1 , . Since 'Co-dominance' is the valid option listed that fits this description, it is the correct answer.