(1) During the mid-1970s, skateboard design changed. (2) Skateboard makers added a kicktail, or raised back end, to the skateboard and substituted sturdy plastic wheels for metal ones. (3) To skateboarders, these changes were welcome improvements. (4) The kicktail made it possible for them to perform new tricks, while the plastic wheels made the board faster and easier to maneuver. (5) With these improvements, skateboarding became more popular than ever in fact it became a worldwide sport. Which is a run-on sentence? sentence 4 sentence 1 sentence 5 sentence 2