Five sealed urns, labelled P, Q, R, S, and T, each contain the same (non-zero) number of balls. The following statements are attached to the urns.

Urn P     This urn contains one or four balls. Urn Q     This urn contains two or four balls. Urn R     This urn contains more than two balls and fewer than five balls. Urn S     This urn contains one or two balls. Urn T     This urn contains fewer than three balls.

Exactly one of the urns has a true statement attached to it.

Which urn is it?