Proteins are A. Compounds containing carbon, hydrogen, oxygen, nitrogen, and usually phosphorus and sulfur B. Compounds containing carbon, hydrogen, oxygen, nitrogen, and phosphorus C. Compounds of t

Proteins are A. Compounds containing carbon, hydrogen, oxygen, nitrogen, and usually phosphorus and sulfur B. Compounds containing carbon, hydrogen, oxygen, nitrogen, and phosphorus C. Compounds of the elements carbon, hydrogen, and much less oxygen