The best way to fix a run-on sentence is to add a comma, conjunction, or period. In this case, separating the sentence into 2 with a period is the best option:
Justin rushed through the obstacle course<u><em>.</em></u> He couldn't make it over the final obstacle in time.
Hope this helps! Good luck! :)
A. Developing a thesis statement
How can i be of assitance fortnite dude? lol
