Answer: 12 carbon atoms
Step-by-step explanation:
Atom is the smallest unit of matter which may or may not have independent existence. Example:

Molecule is the smallest unit of matter which has a independent existence.Example:

1 molecule of
has 6 atoms of carbon
Thus if 1 molecule of
has carbon atoms = 3
4 molecules of
has total of =

Thus there are 12 carbon atoms in four molecules of glucose.