Play stops when the ball carrier's knee, elbow, or any other body part aside from the feet and hands, is forced to the ground (a tackle); when a forward pass is not caught on the fly (during a scrimmage); when a touchdown (see below) or a field goal is scored; when the ball leaves the playing area by any means (being carried, thrown, or fumbled out of bounds); or when the ball carrier is in a standing position but can no longer move forwards (called forward progress). If no score has been made, the next play starts from scrimmage.

Answer this question, if possible (if impossible, reply "unanswerable"): Which touchdown causes play to stop when not caught?
unanswerable