Why is citric acid added to food?
to add color
to add tartness
to add bitterness
to add sweetness

C is wrong, the real answer is B: to add tartness, and the reason why is because citric acid comes from jam, jellies, and more! And that is why the answer B is the correct answer.

Hope this helped!

Nate

(P.S. if you buy jams and real the ingredients, it will say "citric acid." :))

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.