A rigid motion transformation is a type of transformation whereby all the points of the object is moved from one point to another such that the relative distance and the relative position of the points of the object remain the same.
From the options given, the only transformation whereby all the points of the object is moved from one point to another such that the relative distance and the relative position of the points of the object remain the same is hitting a tennis ball over a net.
Therefore, the transformation that describes a rigid body is hitting a tennis ball over a net.