In the following letter series, four letters are missing. Choose the…
2015
In the following letter series, four letters are missing. Choose the alternative whose letters, inserted into the blanks in order, complete the series.
Series: abca _ bcaab _ ca _ bbc _ a
Answer: C. abac — ConceptTo solve a missing-letter series, split the continuous string into blocks and compare how each symbol count changes from one block to the next. A valid…
- A.
ccaa
- B.
bbaa
- C.
abac
- D.
abba
- E.
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Correct answer: C
Concept
To solve a missing-letter series, split the continuous string into blocks and compare how each symbol count changes from one block to the next. A valid completion must make every blank agree with the same rule, not merely fit a local fragment.
Application
The completed structure is abc | aabc | aabbc | aabbcc | a… .
The blocks grow by repeating each leading letter one additional time: abc has one a and one b; aabc has two a letters and one b; aabbc has two a letters and two b letters; aabbcc has two a letters, two b letters, and two c letters.
Reading the four missing positions from left to right gives a, b, a, c.
Cross-check
Substituting abac gives abcaabcaabbcaabbcca, which separates as abc | aabc | aabbc | aabbcc | a. The same progressive repetition holds across all completed blocks.
Therefore, the required letter sequence is abac.