Which one of the following cannot be explained on the basis of Mendel's Law of Dominance ?

The correct option is C Alleles do nt show any blending and both the characters recover as such in $F_2$ generation
Mendel's law of Dominance states that when mating occurs between two organisms of different traits, each offspring exhibit's the trait of one parent only. If the dominant factor is present in an individual, the dominant trait will result. The recessive trait will only result if both factors are recessive.
This law, however, does not occur universally.
Several cases where a clear deviation from the law of dominance was seen was recorded. Such deviations were seen in the form of incomplete dominance and codominance.
Incomplete dominance is a form of intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele. This results in a third phenotype in which the expressed physical trait is a combination of the phenotypes of both alleles.
Codominance is a form of dominance wherein the alleles of a gene pair in a heterozygote are fully expressed. This results in offspring with a phenotype that is neither dominant nor recessive.