Which of the Following Is True Regarding the Milestones of an Infant's

Which of the following is true regarding the milestones of an infant's motor development?

A) At least 50 percent of babies will have attempted walking by 6 months.
B) The age at which one child achieves a milestone does not necessarily predict the age that he or she will achieve the next.
C) The age at which a child first begins to walk predicts the sequence of the rest of their motor developmental trajectory.
D) There is cause for concern if one twin's motor development lags less than a month behind the other.