Which of the following statements is correct?

group of answer choices
a. according to guthrie, reinforcement changes the stimulating conditions and thereby prevents unlearning.
b. according to thorndike, reinforcement is merely a mechanical arrangement that prevents unlearning.
c. according to guthrie, when a response leads to a satisfying state of affairs, its probability of recurring increases.
d. according to thorndike, reinforcement changes the stimulating conditions and thereby prevents unlearning.