Identical Twins Have More Similar Sleep Patterns Than Do Fraternal

Multiple Choice

Identical twins have more similar sleep patterns than do fraternal twins,and people in industrialized nations go to bed later at night than their counterparts of a century ago.These facts best illustrate that sleep patterns are affected by both

A) rapid eye movements and sleep spindles.
B) latent content and manifest content.
C) alpha waves and beta waves.
D) heredity and environment.