The correct option is D MONITOR
From the example given ,
PANCAKE = Q2OD2L10
The code can be deduced as
1, If the letter is a consonant replace it by the next letter in alphabetical order.
2, if the letter is a vowel, multiply the numerical equivalent of that letter by 2 and replace the letter with it
From the code X10MD30N10
Working backwards, for all letters replace it by the letter before it in alphabetical order and for the numbers divide it by 2 and replace it by the vowel corresponding to the resultant It is welcome