Living things require specific organic molecules in order to survive. the picture above represents some specific examples of foods that are mainly composed of one of these necessary organic molecules. the organic molecules found in these types of food are

a)
lipids.

b)
proteins.

c)
nucleic acids

d)
carbohydrates.

Since the illustration is absent the four mentioned are the organic molecules are lipids, proteins, nucleic acids, carbohydrates. These are also called the macromolecules.
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.  

C. the area was covered by water. let me know if this