The answer would be B the method of rock formation
I believe it is D because if the mass is smaller then greater the acceleration for it to be equal force. Hope this helps! Sorry, if I'm wrong.
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Answer:B
Explanation:
Given
mass of Sled is m
another package of mass m is thrown on it
Suppose u be the initial velocity of sled
conserving momentum


where v is the final velocity
Initial kinetic energy 
Final Kinetic Energy
Final Kinetic Energy
Final kinetic Energy is half of initial