Correct Answer: 653

Solution : Given:
1. MOCK ⇒ 9326
2. MINK ⇒ 2538
3. LUNE ⇒ 5041
4. LOUT ⇒ 6714

By comparing all the three coded words, we find that –
In words 1 and 2 the common letter is M/K and the common code is 3/2 .
In words 2 and 3 the common letter is N and the common code is 5 .
In words 1 and 4 the common letter is O and the common code is 6 .
In words 3 and 4 the common letter is L/U and the common code is 4/1 .
The remaining words and codes in word 1 are C and 9 ; in word 2 are I and 8 ; in word 3 are E and 0 ; in word 4 are T and 7 .
Finally, M/K⇒3/2; N⇒5; O⇒6; L/U⇒4/1; C⇒9; I⇒8; E⇒0; T⇒7
So, the code for ONM is 653 or 652 but in option, we have only 653.

Therefore, the code for ONM is 653. Hence, the second option is correct.