A pattern formed by two characters a and b is repeated more than once in the following string:

Mental Ability & Logical Reasoning ·Previously asked in UPSC Civil Services Examination 2026

View the full solved paper: GS Paper II

Question

A pattern formed by two characters a and b is repeated more than once in the following string:

x b x a x a x x a x a x bab

What is x x in the 7th and 8th positions from the left in the above string?

  1. A. aa
  2. B. ab
  3. C. ba
  4. D. bb (Correct answer)

Correct Answer

Option D — bb

Detailed Solution & Explanation

The correct answer is Option D (bb).

Key Points

  • Treat each 'x' in the string as a wildcard to be filled so that a fixed a/b pattern repeats.
  • The 15-character string is the block 'abbab' repeated three times — (abbab)(abbab)(abbab) = a b b a b a b b a b a b b a b — which is consistent with every fixed a and b already shown.

Additional Information

  • Positions 7 and 8 fall in the second 'abbab' block (its 2nd and 3rd letters), both of which are b, so the characters in the 7th and 8th positions are b and b → Option D.