Correct Answer: MLNO

Solution : Let's check the options –

First option: HJKL → H + 2 = J, J + 1 = K, K + 1 = L

Second option: PRST → P + 2 = R, R + 1 = S, S + 1 = T

Third option: MLNO → M – 1 = L, L + 2 = N, N + 1 = O

Fourth option: ACDE → A + 2 = C, C + 1 = D, D + 1 = E

So, the difference between letters in the other options except the third one is in a consistent order.

Hence, the third option is correct.