Final answer:
George is trying to estimate the A) heritability of height by determining how much of height variation is due to genetic factors as opposed to environmental influences.
Step-by-step explanation:
George is attempting to estimate the A) heritability of height. Heritability refers to the proportion of difference among people that we can attribute to genetic differences, and is a measure of how much of the variation in a particular trait, in this case height, within a population is due to genetic factors.
By studying European males, George wants to understand the genetic variance affecting height. Environmental factors also influence the expression of the genotype, and thus the phenotype, but the heritability specifically looks at the genetic contribution to the variation.
Factors such as nutrition can influence height but would fall under environmental influences rather than genetic factors.
Observing identical twins, including those who have been reared apart, has been vital in behavioral genetics to estimate the influence of genes versus the environment on various traits, including height.