Given what we know about the operation of the phonological loop, which of the following word lists would be most difficult for people to retain for 15 seconds?
a. SAY, BET, PIN, COW, RUG
b. BIP, TEK, LIN, MOD, REY
c. MAC, CAN, CAP, MAN, MAP
d. PIG, DOG, RAT, FOX, HEN