All the biological macromolecules contain Carbon, hydrogen and oxygen. However, most do not contain nitrogen. The category that contains nitrogen are A) lipids. Eliminate B) proteins. C) carbohydrates. D) unsaturated fats.

The correct answer is B. Proteins. Proteins almost always contain nitrogen and are essential for our well being. Without them there would be no humans because we would all die which is why their correct synthesis in the cell is of extreme importance. Besides all the regular things like carbon, they also have nitrogen very often.