Correct option is B. Law of segregation
According to the law of dominance, a trait is represented by two contrasting factors of a gene in a heterozygous individual but the only dominant trait is expressed and recessive one is masked by the presence of dominant allele. Incomplete dominance and co-dominance are the exception to the law of dominance. Law of segregation states that the two factors for a trait, present together in a heterozygous individual, do not get mixed and are separated during gametogenesis. Segregation of chromosomes of a homologous pair during meiosis followed by their distribution to gametes singly ensures its universal acceptance without any exception. Law of independent assortment tells about segregation and distribution of factors governing two different traits. The tendency of closely placed genes on a chromosome to stay together during inheritance i.e. linkage and therefore no independent assortment make the linked traits exception to the law of independent assortment. According to the principle of a unit factor, each character is governed by a pair of the discrete unit, called factor or genes. Multiple alleles serve as an exception to this rule. Thus, the correct answer is option B.