A man getting down a running bus falls forward because
Due to inertia of motion upper part of the body continues to be in motion in forward direction while feet come to rest as soon as they touch the road
Explanation for correct option:
In case of option B,
Explanation for incorrect options:
In case of option A,
In case of Option C,
The habit of leaning forward is not relevant to laws of motion.
In case of option D,
Option D will be correct when all three options will be correct. Here only option B is correct and option A and option C are incorrect, thus option D is also incorrect.
Hence, option B is the correct answer.