Choose the correct alternatives.
abca_bcaab_ca_bbc_a
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → abac
Filling the four gaps in order with a, b, a and c gives the complete series a b c a a b c a a b b c a a b b c c a.
Broken up, it reads abc / aabc / aabbc / aabbcc — each group repeating the letters a, b and c with one more of them appearing in turn, which is the pattern the series follows. None of the other sets produces such a regular progression.