Which one of the following options will express intermediate skin colour in an individual?

The correct option is AaBbCc.

Human skin color is a classic example of polygenic inheritance, which is controlled by three or more pairs of non-allelic genes. In this case, skin color is determined by three genes: A, B, and C.

Each of these genes has two alleles. The dominant alleles (A, B, and C) contribute to dark skin color by promoting the synthesis of melanin, while the recessive alleles (a, b, and c) contribute to light skin color (lack of melanin).

The phenotype (physical appearance) of an individual depends on the total number of dominant alleles inherited:
- A genotype with all six dominant alleles (AABBCC) results in the darkest skin color (negro).
- A genotype with all six recessive alleles (aabbcc) results in the lightest skin color (albino/very light).
- An intermediate skin color, also known as a mulatto phenotype, is produced when there is an equal distribution of dominant and recessive alleles, meaning exactly three dominant alleles and three recessive alleles are present.

Let us analyze the genotype given in the correct option:
The genotype is $AaBbCc$.
Counting the alleles in $AaBbCc$:
Dominant alleles = 3 (A, B, C)
Recessive alleles = 3 (a, b, c)

Since this heterozygous genotype contains exactly three dominant and three recessive alleles, it represents the perfect intermediate blend of the two extremes, thus expressing intermediate skin colour.