3. Wharton or Harvard is my preference; however, I’ll attend any school that accepts me.
Explanation:
The subjective "Wharton or Harvard" being singular must agree with the singular form of the verb "is," and not the plural form of the verb "are." In the same way, the singular form of the subject "school" must agree with the singular form of the verb "accepts" and not the plural form "accept." This is grammatically described as "concord," which is the agreement of subject and verb.
