Comes from a source within a film's world and could be heard by characters is the correct answer.
Explanation:
Diegetic sound is defined as a noise that comes from the screen; some examples are dialogs from other people, footsteps, motors, and so on. Since it comes from the screen itself, characters can listen to it but they don't have to react to it. Diegetic sound is different from Non-diegetic, since this last one refers to the sounds that don't come from the screen, such as music or special effects.
D. Mississippi because onomatopoeia is when the word is the same as the meaning. boom means boom, pew means pew, cackle means cackle. Basically onomatopoeia is sounds
