In the game of space billiards with albert at rest, henry’s space ball changes vertical velocity less than albert’s. albert believes in the conservation of momentum, so he believes for momentum to be conserved,
a. the collision must be elastic
b. the mass of henry’s space ball must be less than his
c. the mass of henry’s space ball must be equal to his
d. the mass of henry’s space ball must be greater than his

The momentum an object has may be computed using the product of the object's mass and velocity.
If Albert and Henry gained the same amount of momentum, then the product of their respective mass and velocity will be the same.

However, this does not mean that their masses and their velocities are equivalent to one another. Therefore, if Albert's ball gained less velocity than Henry's, then Albert's ball must have a greater mass.

The answer is B.