Two masses collide and stick together. Before the collision one of the masses was at rest. Is there a situation in which the kinetic energy is conserved in such a collision?

A、Yes, if the less massive particle is the one initially at rest.;
B、Yes, if the more massive particle is the one initially at rest.;
C、Yes, if the two particles have the same mass.;
D、No, kinetic energy is always lost is such a collision.