Q.Which one of the following is an example of polygenic inheritance?

Polygenic inheritance is the pattern in which several different genes, each typically with two or more alleles, act together in an additive way to determine a single trait, producing continuous (quantitative) variation rather than a small number of sharply distinct classes. Swedish geneticist H. Nilsson-Ehle gave the first experimental demonstration of this in 1909, using wheat kernel colour: crossing dark red (R1R1R2R2) with white (r1r1r2r2) wheat gave a medium-red F1, and the F2 generation showed kernel-colour intensity tracking directly with how many 'R' alleles (of either gene) a plant carried - each R allele adding a fixed increment of red pigment. Plotting individuals against colour intensity produces the characteristic bell-shaped curve of …