Did the website specify who recommendations should come from? Every MOC has a website that will have a link for SA nominations. Follow it exactly. Many are similiar, but will vary slightly.
If not, who do you think knows your well enough to speak about your character, drive, leadership ability, motivation, etc. Coaches, teachers, scout leaders, youth leaders, etc. Usually the directions are pretty clear on who they want letters from, if not, use your best judgement on who knows you well and can speak to your strengths and knows you well.