The right option is d) bubbles
The production of bubbles when baking soda mixes with an acid such as vinegar is the observation that indicated a chemical property of the baking soda.
Baking soda (also known as sodium bicarbonate) is a nonflammable, white crystalline powder. Baking soda is odorless, and alkaline. Baking soda reacts with vinegar (acetic acid) to produce carbon dioxide (a gas), water, sodium ion and acetate ion. Baking soda is used for many purposes such as; as an antacid for treating indigestion, for baking, in fire extinguishers, as a water softener, as a pesticide, and to remove dirts from materials.