Answer:
Option A
Explanation:
1st letter : $P-1 \rightarrow O, O-1 \rightarrow N, N-1 \rightarrow M, M-1 \rightarrow L,$
2nd letter : $M+2 \rightarrow O, O+2 \rightarrow Q, Q+2\rightarrow S, S+2\rightarrow U$
3rd letter : $T-1 \rightarrow S, S-1 \rightarrow R, R-1 \rightarrow Q, Q-1 \rightarrow P$
Hence the answer is (a).