Which of the following chemical compound is used as a preservative in pickel?

Sodium Benzoate

The correct answer is option 3. Sodium Benzoate.

The chemical compound commonly used as a preservative in pickles is Sodium Benzoate.

Sodium benzoate is frequently used as a preservative in acidic food products such as pickles to prevent the growth of bacteria, fungi, and yeast. Therefore, option 3, Sodium Benzoate, is the correct answer.