While roller-skating, Granny collides with her tiny grandson Ambrose who is at rest. Ignoring any friction effects, Amobrose's speed after the collision will be greater when

A. Granny catches him and they both move together.

B. He and Granny make a bouncing collision, each going in opposite directions.

Remember in the text about that "bounce" affect (consider the water wheel and its shape to allow the water a longer contact time to move the wheel faster). The energy transferred with the bouncing collision is far greater than both moving together in the same direction.