According to the passage, "infralimbic neurons … fire to the tone only when rats are recalling extinction on the following day" (lines 7-9) for which of the following reasons

(A) Extinction has not been proven to erase the memory of fear conditioning in rats.
(B) The extinction response requires a number of days to develop.
(C) The subject’s original fear response was not conditioned to a tone.
(D) The infralimbic cortices carry the memory of fear extinction.
(E) Rats that show the least fear demonstrate the greatest increase in infralimbic tone responses.