$\begin {array} {1 1} (a)\;Kinetic\: energy\: changes\: but\: momentum\: is\: constant \\ (b)\;Momentum\: changes\: but\: kinetic \: energy \: is\: constant \\ (c)\;Both \: momentum\: and\: kinetic\: energy\: remain\: constant \\ (d)\;Both\: momentum \: and \: kinetic\: energy\: change \end {array}$