Leroy Is Hopi and Started to Walk at 19 Months

Leroy is Hopi and started to walk at 19 months. What is the most likely explanation for his late onset of this motor milestone?

A) Hopi have a different genetic make-up that has been associated with delayed motor milestones.
B) Hopi often use cradle boards to constrict their infants which might delay their motor development.
C) Hopi do not allow their infants to walk to allow their muscles and bones to become stronger.
D) Leroy's father was a late walker himself and his son inherited this trait.