In an elastic collision between two bodies, during the time collision is taking place, which physical quantity is conserved?

Question

$$\begin {array} {1 1} (a)\;KE & \quad (b)\;momentum \\ (c)\;both\; momentum\; and\; kinetic \;energy & \quad  (d)\;none\;of\;the\;above \end {array}$$

Comments

what is the answer