A Popular Swinging-Balls Apparatus (Newton's Cradle)consists of a Series of Identical

A popular swinging-balls apparatus (Newton's cradle) consists of a series of identical elastic balls suspended by strings so they barely touch each other.When two balls are pulled away from one end and released,they strike the row of balls and two balls pop out from the other end.If instead,one ball popped out with twice the speed,this would violate the conservation of

A) momentum.
B) energy.
C) both of these
D) none of the above