Answer: A) Subjunctive.
Step-by-step explanation: Subjunctive is a mood of verbs or a verb form that denotes something that is not a fact but a possibility or a desire. In the given sentence "Student Council expects that everyone participate in Sunglasses Day" we can see a clear example of subjunctive mood in the underlined verb "participate" because it isn't a fact that everyone will participate, it is just something that could happen.