The correct option is B Factors reside in chromosomes
When Mendel performed the experiments and deduced the laws (Law of Dominance, Law of segregation and Law of independent assortment) he used the term 'factors' for the elements responsible for the phenotype of an organism. We now call them 'genes'. Mendel gave the laws of inheritance of these factors but he did not know that they are present on chromosomes. This theory called chromosome theory of inheritance was given by Boveri and Sutton during 1902-1903.