7.6 Medium

A. Intelligence is almost entirely determined by the environmental stimulation received during childhood, as evidenced by the similar IQs of twins raised together.

B. Both genetic and environmental factors contribute to intelligence, but genetics play a significant and measurable role, even when environmental influences differ.

C. The study is inconclusive regarding the source of intelligence, as identical twins share both genetics and often similar environments, making it impossible to separate influences.

D. Environmental factors are the sole determinants of intelligence, and the high correlation in identical twins' IQs is purely coincidental.

E. Intelligence is a mutable trait, completely shaped by life experiences, with no discernible genetic predisposition.