A Puck of Mass M₁ and Initial Velocity V₁ Collides

A puck of mass m₁ and initial velocity v₁ collides elastically with a second puck of mass m₂, which is initially at rest. After the collision, m₁ moves with velocity v₁' at an angle below the x axis) and m₂ moves with velocity v₂' at an angle above the x axis) . The conservation of momentum along the x direction can be written as

A) m₁ v₁ = m₁v₁' cos + m₂v₂' cos) .
B) 0 = m₁v₁' cos + m₂v₂' cos) .
C) m₁ v₁ = m₁v₁' sin + m₂v₂' sin) .
D) 0 = m₁v₁' sin + m₂v₂' sin) .
E) none of the above