its b.)Student receives a piece of candy after answering a question correctly in class. since the student is being rewarded in return for a correct answer, so the student will proceed to try to answer correctly to get the candy; a stimulus response. though the last sentence might be right, it doesn't grant a reward, only verbally, it serves as motivation and pride, but not a reward. the other two are unrelated to the law of effect so they aren't an option to consider.
-hope it helps!
