Which Statement Best Describes Cross-Cultural Development of Motor Skills

Which statement best describes cross-cultural development of motor skills

A)  Rates vary somewhat across cultures, suggesting that genetic factors can slow or accelerate early motor development. 
B)  Rates do not vary across cultures, suggesting that genetic factors alone determine early motor development. 
C)  Rates do not vary within cultures, suggesting that environmental factors alone determine early motor development. 
D)  Rates vary somewhat across cultures, suggesting that environmental factors can slow or accelerate early motor development.