Ineed on #5 idk remember very well what my bio teacher said

in a chemical reaction, the atoms and molecules produced by the reaction are called products. no new atoms are created, and no atoms are destroyed. in a chemical reaction, reactants contact each other, bonds between atoms in the reactants are broken, and atoms rearrange and form new bonds to make the products.

i think the answer is a.keratin is the pigment responsible for skin color.