A man getting down a running bus, falls forward because

• A.  due to inertia of rest, road is left behind and man reaches forward
• B.  due to inertia of motion upper part of body continues to be in motion in forward direction while 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]