the answer is B my mom is a doctor and she helped me on this once
1) Exercise it by singing and hitting different notes, however don't go overboard
2) Make sure you don't overuse your voice, as well as trying to rest your voice when you are sick
3) Overall, have healthy habits, like not smoking and drinking a sufficient amount of water.
A protein is made up of a chain of amino acids.
The answer is German measles