Final answer:
An example of a phenotype is the observable eye color of an individual. Phenotype is determined by the interaction of genes and environment and is distinct from genotype, which is the genetic makeup of an organism.
Step-by-step explanation:
The description that is an example of a phenotype is c) The observed eye color of an individual. A phenotype refers to the observable traits expressed by an organism, such as hair color, eye color, height, and build. These traits result from the interaction of the individual's genotype—the combination of alleles—and the environment. The genotype, on the other hand, is the genetic makeup of an individual and consists of the DNA sequence of genes including both expressed and non-expressed alleles. Therefore, both options a) The presence of an allele for eye color and d) The DNA sequence of a gene would be examples of genotype, not phenotype.