Infants whose parents help them practice specific locomotor skills, such as sitting upright on their own, tend to develop those specific skills

a. later than infants who were not given any assistance
b. earlier than infants who did not receive any assistance
c. at the same time as infants without practice or assistance
d. and other locomotor skills, such as pulling themselves to a standing position, earlier than infants who are not given additional experience with any of those skills

B