Whenever there is a collision between two bodies, the total momentum of the bodies remains conserved. If after the collision of two bodies, the total kinetic energy of the bodies remains the same as it was before the collision, then it a perfectly elastic collision. A ball bearing striking another ball bearing is an example of elastic collision.
If two bodies stick together after the collision, then the collision is said to be perfectly inelastic collision.
Options (a), (b), (c) are examples of inelastic collision