ABO blood group has:
1.  Two codominant and one recessive allele
2.  Two codominant and two recessive allele
3.  Two incompletely dominant genes
4.  Two pseudo alleles

The ratio of complementary genes is:
1.  9 : 3 : 4
2.  12 : 3 : 1
3.  9 : 3 : 3 : 4
4.  9 : 7

Two nonallelic genes produce the new phenotype when present together but fail to do so independently then it is called:
1.  Epistasis
2.  Polygene
3.  Non-complimentary gene
4.  Complimentary gene