Contestants are running. This sentence contain a subject verb agreement. Subject - contestants; verb - are running. These words put together forms a complete thought.
Agreement rule applies to a subject joined by OR or NOR is make the verb agree with the subject closest to the verb.
OR / NOR Rule states that Singular subjects joined by OR or NOR are singular. Plural subjects joined by OR or NOR are plural.
So if the subject is singular, the verb must be in singular form if joined by OR or NOR. If the subject is plural, the verb must be in plural form if joined by OR or NOR.
