Consider the following statements. (a) Genetical basis for blood types in human beings is due to the presence of three types of alleles IA, IB, IC. (b) Mendel initially concentrated on the results of two traits at a time. (c) When the inheritance of two traits is considered, they are inherited independently of each other. (d) If parents differing in only one trait were crossed, it is called dihybrid cross. Which of the above statements is/are correct?