Genotypic and phenotypic ratio, 1:2:1 in the offsprings explain the principle of

The correct option is B blending inheritance
Blending inheritance states that progeny inherits characters as the average of the parents' characters. This theory was discarded with the acceptance of Mendelian inheritance.

The theory of blending inheritance is similar to the inheritance of incomplete dominance as shown by snapdragon/dog flower. In snapdragon, plants with white flowers when crossed with plants with red flowers, give rise to progeny with pink flowers. The phenotypic and genotypic ratios are same (1:2:1) in this condition as shown below.