Correct Answer: K

Solution : Given:
DE : O :: AF : ?

Multiply the sum of the position values of the letters of DE by 2 and then subtract 3 from it to get the required code –
The position value of DE; D→4, E→5
DE→(4 + 5) × 2 = 9 × 2 = 18
Now, subtract 3 from it→18 – 3 = 15→O
Thus, DE is coded as O.
Similarly, follow the same pattern for AF –
The position value of AF; A→1, F→6
AF→(1 + 6) × 2 = 7 × 2 = 14
Now, subtract 3 from it→14 – 3 = 11→K
Thus, AF is coded as K.

Only the second option follows the same pattern as followed by the given pair. Hence, the second option is correct.