Final answer:
Flower position in plants is an example of a phenotype, which is the observable expression of a genetic trait.
Step-by-step explanation:
Flower position is an example of an observable characteristic, or in other words a phenotype. Phenotypes are the physical expressions of traits that result from the interaction of alleles (different forms of a gene).
In the context of Mendel's experiments with pea plants, traits like flower position, flower color, and seed texture were among the seven characteristics he observed. For instance, seed color was one characteristic Mendel studied, and he found that the yellow-seed allele is dominant over the green-seed allele, which is an aspect of the phenotype of the plants.
Thus, the correct answer to the statement 'Flower position is an example of which of the following?' is d) Phenotype.