A 1-Kg Glider and a 2-Kg Glider Both Slide Toward

A 1-kg glider and a 2-kg glider both slide toward each other at 1 m/s on an air track.When they collide and stick,the combined-glider speed is

A) 0 m/s.
B) 1/2 m/s.
C) 1/3 m/s.
D) 1/6 m/s.
E) 1.5 m/s.