Which of the following is most stable

The most stable anion is that which is present near the most electronegative element.

The most stable anion is that which is delocalised and forms a resonating structure.

The most electronegative elements are F,O,N.

In option (A) lone pair is not delocalised so it is not stable.

So the most stable anion is in option (D).

Hence the correct answer is (D)