Genetics

The correct option is (D): 3:1.

Allosomes, also known as sex chromosomes, are the chromosomes that determine the biological sex of an organism. In humans, there are two allosomes (X and Y), which can combine in different ways to produce male (XY) or female (XX) offspring. Thus, the number of allosomes in human cells is 4 in the case of a male (XX or XY) cell pair.

In a monohybrid cross, the typical phenotypic ratio in the F2 generation is 3:1, where three individuals exhibit the dominant trait, and one individual exhibits the recessive trait. This follows Mendel's laws of inheritance.