Dally chooses to die because deep down inside, he cannot live without Johnny and the pain of his death and not having Johnny around anymore is just too much to bear. He also feels in some way, a little guilty. In a way, his act was a bit cowardly. His friends have to live with the death of Johnny, just like he would if he didn't die. Now his friends have to live with the death of Dally too.
Assuming that you're referring to the Flvs english 1, the one that you need to think bout throughout unit 1 is : Future possibilities. Most of the topic in this unit talk about future possibilities
Answer:
From the Words, Mood, Lesson Learned, the way it makes you fee, the description and the setting.