<i>In the question below choose the word(s) or phrase(s) which <b>best fills(s)</b> the gap(s)</i>:If only Adoyi .... what was good for him he could easily have avoided the tragedy

In the question below choose the word(s) or phrase(s) which best fills(s) the gap(s): If only Adoyi .... what was good for him he could easily have avoided the tragedy

In the question below choose the word(s) or phrase(s) which best fills(s) the gap(s):

If only Adoyi .... what was good for him he could easily have avoided the tragedy

The correct answer is D. had known

No explanation given