Clearly, to obtain the code, the first letter of the word MENTION is moved one step backward and the remaining letters are reversed in order, taking two at a time.
(M → L), (E ↔ N), (T ↔ I), (O ↔ N)
So, in  PATTERN, P will be coded as O and the sequence of the remaining letters in the code would be TAETNR.
Thus, the code becomes OTAETNR.
Hence, the answer is (c).