If MILD is coded as NKOH, which code should replace the question mark below?…

Concept: This is a letter-shift coding-decoding puzzle. Each letter of the code word is obtained by shifting the corresponding letter of the plain word forward in the alphabet, with the shift amount increasing by 1 for every successive letter: the 1st letter shifts by +1, the 2nd by +2, the 3rd by +3, and the 4th by +4.

Application: First confirm this rule against the given pair, then apply the same shifts to GATE:

1. Verify with the given pair: M(+1)=N, I(+2)=K, L(+3)=O, D(+4)=H, which reproduces NKOH exactly — confirming the shifts +1, +2, +3, +4.

2. Apply the same shifts, in the same order, to G, A, T, E: G(+1)=H.

3. A(+2)=C.

4. T(+3)=W.

5. E(+4)=I.

Cross-check: Reverse the same shifts from the result by subtracting +1, +2, +3, +4: H(-1)=G, C(-2)=A, W(-3)=T, I(-4)=E, which reconstructs GATE exactly, confirming the coding is consistent both ways.

Result: So GATE is coded as H C W I, following the same steadily increasing shift pattern confirmed by MILD : NKOH.