Concerning Infant Movement

Concerning infant movement,

A) initial modes of movement vary greatly, but by about 10 months most infants are crawling on their hands and knees
B) initial modes of movement vary greatly, but by about 10 months most infants are walking
C) the initial mode of movement almost always involves rolling, but by about 10 months most infants are crawling on their hands and knees
D) the initial mode of movement almost always involves rolling, but by about 10 months most infants are walking