Consider the following arrangement that has some missing letters:
abab_b_bcb_dcdcded_d
The missing letters which complete the arrangement are
Answer & explanation
Answer: (c) a, c, c, e
With a, c, c, e filled in, the string splits into four blocks of five letters — ababa, bcbcb, cdcdc, deded — each alternating two neighbouring letters. No other option gives a regular pattern.
- The completed string has 20 letters; try blocks of 5.
- Fill a, c, c, e: a b a b a | b c b c b | c d c d c | d e d e d.
- Each block alternates two consecutive letters (ab, bc, cd, de), starting where the last block ended.
- Check option (d) b, c, d, e: the first block becomes ababb, which breaks the alternation.
Remember · For letter-gap series, try splitting the full string into equal blocks; the blank count and length often reveal the block size.
Question and answer: UPSC's official GS Paper II (2020, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·