The largest molecules in organisms are carbohydrates proteins lipids nucleic acids

Nucleic Acids is the largest molecules in organisms.

Macromolecules are a set collection of polymers that composes most of the organic substances specifically in the organelles of cells. Thus, these organelles use lipids and proteins in doing cellular activity and keeps them functioning. Observe nitrogen and carbon, these two entities are called elements that are composed of atoms. Elements are the basic composition of a substance. Going back, examples of molecules could be nucleic tides, polypeptides, RNA, protein, lipids and etc.  

The answer is option e. it protects the heart and lungs.