Which of these is a run-on sentence?
Elijah planned to visit his friend for the weekend. He put his toothbrush and his favorite game in his backpack.
Elijah planned to visit his friend for the weekend, so he put his toothbrush and his favorite game in his backpack.
Elijah planned to visit his friend for the weekend. Therefore, he put his toothbrush and his favorite game in his backpack.
Elijah planned to visit his friend for the weekend, he put his toothbrush and his favorite game in his backpack.