Mary was challenged by her friend, kate, to memorize 15 letters, c, i, a, c, b, s, a, b, c, f, b, i, i, r, and s, in the same order, within half a minute. mary arranged these alphabets into groups: cia, cbs, abc, fbi, and irs. this made it easier for her to meet kate's challenge. in this scenario, mary has used the tactic of _____.