Tartaric acid is a common edible acid used as a component of baking powder. It reacts with the baking soda (sodium bicarbonate) in the presence of moisture and heat to produce carbon dioxide gas, which causes baked goods to rise and become fluffy. It is also used industrially as an acidulant in many food products, including carbonated soft drinks, fruit jellies, and candies.

B. fatty acid: Fatty acids are carboxylic acids with long aliphatic chains and are a major component of fats and lipids. They are not used as an acidulant in soft drinks or as a component in baking powder.

C. boric acid: Boric acid is a weak acid often used as an antiseptic, insecticide, or fire retardant. It is not an edible acid used in food products like baking soda or soft drinks.

D. citric acid: While citric acid is a very common acidulant in soft drinks and other food products, where it provides a sharp, tangy flavor, tartaric acid is the option specifically associated with both baking soda (as a baking powder component) and soft drinks.

The correct answer is tartaric acid - option A