Answer:
c.Alleles
Step-by-step explanation:
Genes are the hereditable units that transmit the information needed to specify traits (such as hair or eyes color), from parents to offspring, generation to generation. Genes are arranged in sequence in the chromosomes. A chromosome might contain hundreds of thousands of genes.
Each chromosome carries specific genes that code for specific proteins that have specific functions in the organisms. Each chromosome carries information to synthesize different proteins needed to accomplish a certain function. But not all chromosomes carry the same gene sequences. Only homologous chromosomes carry information for the same trait, but even this information is not necessarily the same. They might have the same gene but in different alternatives.
Alleles are the different alternatives in which a gene might appear. By the process of natural mutation, a gene might change into two or more alternative forms that are called alleles. These alternative forms codify for the same trait expressing different phenotypes.
In the exposed example, alleles are responsible for the different phenotypes expressed by the girls. The alternative forms of the genes -the alleles- that codify or hair color and for eyes color, express either red or blonde hair, and either blue or brown eyes.
The final genotype and phenotype depend on the gametes that merge to form the zygote, and hence the new organism.