Choose the correct alternatives.
abca_bcaab_ca_bbc_a
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → abac
Filling the blanks in turn with a, b, a, c gives a series built from abc, with one more letter doubled in each new group:
abc
aabc (a doubled)
aabbc (b doubled as well)
aabbcc (c doubled as well)
a (the next group begins)
Written out, the series is abcaabcaabbcaabbcca, and the four filled letters are a, b, a, c.