Answer: C. You are class valedictorian and you are speaking at graduation.
Step-by-step explanation:
Formal speech is referred to as a form of speech that's given in a formal setting and intended to show sense of decorum. During formal speech, slangs or friendly tone are not used.
Based on the options given, the situation that would make the most formal speech is "You are class valedictorian and you are speaking at graduation'