Which of the following is an example of vicarious reinforcement?

a. babs saw martin receive a candy bar for completing his reading list. she is careful to complete her reading list because she saw martin get a reward for doing it.
b. lana wants to receive a candy bar and she knows from reading the rulebook that she will receive one if she earns enough good behavior tokens.
c. park wants to avoid detention, so he follows the school rules and does not smoke on the playground.
d. ryan observes cameron getting a time out for spitting out her toast. because he saw his friend punished, he does not spit out his toast.