Question

Which situations describe an elastic collision?
Two glass marbles bounce off each other.
Rodrick flops onto his sofa and sinks into the cushion.
A tossed water balloon flattens when it lands on the grass.
A bowling ball knocks over five pins.

Answer 1

in an elastic collision, KE is preserved before and after the collision, and the objects involved "bounce" off each other

there are 2 choices from the list that match this description, try to determine which ones they are