What do all four of these molecules have in common?

A.

They are essential to life.

B.

They carry signals.

C.

They are water soluble.

D.

They act as a source of energy

I did a quick search and found the diagram. Let's go through these and solve by elimination.

B. Proteins can act as receptors which I guess could be considered a signal, but the rest of the molecules do not. B is incorrect.

C. Lipids are not water soluble. An example of lipids are fats, and oils. Have you ever tried combining water and oil? Think about salad dressing, it does not mix. C is incorrect.

D. Carbohydrates and lipids are sources of energy, but nucleic acids and proteins are not. D is incorrect.

The answer is A. because we know that our bodies are made up of nucleic acids, protein, fats, and we need carbohydrates in order to live normal, healthy lives.

A. They are Essential to Life