The correct answer is option B a molecule.
Cells are the basic structural and functional units of living organisms. If a bunch of keys represents a cell, each key in the bunch represents a molecules. The levels of organization in an organism is as follows.
atom ⇒ molecule ⇒ cell ⇒ tissue ⇒ organ ⇒ organ system ⇒ organism.
Molecules represent the keys in a key bunch. A molecule is made up of one or more atoms held by chemiclal bonds. A cell is made up of various biomolecules. The cell wall consists carbohydrates, cell membrane consists of fats and proteins, the cytoplasm of the cell consists of water molecules, proteins, fats, carbohydrates and the nucleus has the biomolecules called the nucleic acids. Thus, many such biomolecules make up a cell.
