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
(a) self-reference (learned by own experience)
(b) chunking
(c) rehearsal (looking over it a lot)
(d) priming

The right answer is option B „chunking”

Explanation:

Chunking is the process in which we take separate pieces of information, named as chunks, and we group them in bigger items because this way the information given will be easier to retain, as well as we can remember more. This is because our short-term memory just allows us to keep in mind, according to various studies, between four or nine chunks of information, so for Mary will be easier to retain 5 groups of 3 letters than 15 individual letters.  

balearic sea - is a body of water in the mediterranean sea around the balearic islands. baltic sea - is a mediterranean sea of the atlantic which is enclosed by scandinavian and baltic countries. barents sea - is a marginal sea in the artic ocean located off the northern coast of norway and russia.

hygrometers and hair thermometers (often found as part of hygrometers/psychrometers) can be used to measure humidity. barometers are used to measure atmospheric pressure, while anemometers are used to measure wind speed. so the 2nd and 4th choices should be the correct answers.