In the following question, select the related letter/letters from the given…

In a letter/alphabet analogy of this type, the relationship between the two words in the first pair is a fixed rearrangement of positions — each letter keeps its identity but moves to a new position in the word — not a letter-by-letter alphabet shift. To solve it, first find exactly which position moved where in the given pair, then apply that same position mapping to the second word.

From NEST : SETN, tracking where each position moves:

Applying the same idea to NTPC:

1. Labelling the positions of NEST as 1-2-3-4 = N-E-S-T: position 2 (E) stays fixed while positions 1, 3, and 4 change places, producing S-E-T-N (shown above).

2. Labelling the positions of NTPC as 1-2-3-4 = N-T-P-C, the identical position mapping applies (shown above).

3. Position 2 (T) stays fixed while positions 1, 3, and 4 rearrange identically, producing the new order P, T, C, N.

This checks out: P, T, C, N uses exactly the same four letters as N, T, P, C with no repeats or omissions — confirming only positions were rearranged, exactly as in NEST to SETN.

Therefore, the correct answer is "PTCN".