(a) "Everyone are" is wrong. "Everyone" is an indefinite pronoun and stands as singular. Therefore, we should say "everyone is" instead.
(b) "They talks" is wrong. "They" is pronoun referring to many people. Therefore, we should use the appropriate verb and say "they talk" instead.
(c) "Contestants are running" is correct. "Contestants" is a plural noun and needs a plural verb. "Are" is in the plural form of a verb.
(d) "Krumpers prepares" is wrong. "Krumpers" is a plural noun and needs a plural verb. Therefore, we should say "krumpers prepare" instead.
