At Time T = 2

At time t = 2.3 s, a 4-kg block that initially moves with a constant speed of 6 m/s undergoes an inelastic collision with another block. Any two inertial observers must agree that

A) the event took place at t = 2.3 s.
B) the initial speed of the block is 6 m/s.
C) the initial momentum of the block has magnitude 24 kg . m/s.
D) the second block is moving after the collision.
E) the momentum of the two block system is conserved during the collision.