A particle of mass M1 makes an elastic, one-dimensional collision with a stationary particle of mass M₁. what fraction of kinetic energy of M₁ is carried away by M₂?
(A) M₁/M₂
(B) M₂/M₁
(C) 2M₁M₂/(M₁+M₂)sq.
(D) 4M₁M₂/(M₁+M₂)sq