Step 1: Understand the inheritance in Mirabilis jalapa. Mirabilis jalapa (Four o’clock plant) exhibits incomplete dominance, a condition where the dominant allele is not completely dominant over the recessive one.
Example: When a red-flowered plant (RR) is crossed with a white-flowered plant (rr), the F1 generation consists of plants with pink flowers (Rr) — an intermediate phenotype.
Step 2: Match with the options. Option (1) ABO blood group – shows codominance (IA and IB are codominant). Option (2) Flower colour in snapdragon – also shows incomplete dominance, just like Mirabilis jalapa. Option (3) Fur colour in rabbit – influenced by multiple alleles. Option (4) Skin colour in humans – is a polygenic trait.
Step 3: Conclusion. Since both Mirabilis jalapa and snapdragon exhibit incomplete dominance, option (2) is correct.