Answer:
The correct answer would be protein as a source of amino acids.
Explanation:
Proteins are the major source of amino acids. These are said to have a key role in building muscle mass. Proteins can be obtained from the egg, red meat, tofu and cheese, and other sources. Potassium is also a great muscle building nutrient.
In different protein supplements L-leucine, L-isoleucine and L-valine, branched-chain amino acids are present which is used by bodybuilders.
Thus, the correct answer would be Protein.
