Correct option is D
Given,
KL91 → CD66
MN81 → EF56
OP71 → ?
Logic: each term in first and second letter is decrease by 8 and third number is decrease by 25.
KL91 → CD66
K → C (-8), L → D (-8) → 91 → 66 (-25)
MN81 → EF56
M → E (-8), N → F (-8) → 81 → 56 (-25)
Similarly,
OP71 → ?
O → G (-8) → P → H (-8) → 71 → 46 (- 25)
The missing number is 46.
Thus the correct answer is: Option D