$A$ man getting down from a running bus falls forward because:

• A
  Due to inertia of rest,the road is left behind and the man reaches forward.
• B
  Due to inertia of motion,the upper part of the body continues to be in motion in the forward direction while the feet come to rest as soon as they touch the road.
• C
  He leans forward as a matter of habit.
• D
  Of the combined effect of all the three factors stated in $(a)$,$(b)$,and $(c)$.