Centre of Mass and Collision Part 1

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A Body P having mass M moving with speed u has head-on collision elastically with another body Q having mass m initially at rest. If m≪M , body Q will have a maximum speed equal to 2u after collision.
Reason R During elastic collision, the momentum and kinetic energy are both conserved.
In the light of the above statements, choose the most appropriate answer from the options given below.