Identical twins were separated at birth and raised by two different families. Years later, one twin was a physically fit member of the cross-country team, and the other twin was overweight with slightly higher-than-normal blood pressure. The differences in these twins could be explained by the fact that 1. the genes in the two individuals are completely different 2. in twins, each individual inherits genes from only one parent 3. the DNA bases in twins combine differently 4. the environment can influence the expression of genes.