A. Fibrous
B. Membrane
C. Globular
D. Unsaturated
There are three types of proteins: fibrous, membrane, and globular. Fibrous or structural proteins consist of collagen, elastin, and keratin. Membrane proteins are interactive and anchored to a membrane. Globular proteins consist of functional proteins like enzymes, hemoglobin, and insulin.
Therefore unsaturated is the correct answer.
Therefore, the Correct Answer is D.