Answer: The basic unit of a sugar molecule is carbon.
Step-by-step explanation:
Carbon forms the skeleton of all sugar molecules. It is the basic unit of every sugar molecule which has the ability to form covalent bonds with other elements like hydrogen and oxygen to form sugar molecules. For instance, in a simple sugar such as glucose having a formula of C6H12O6, carbon combines with hydrogen and oxygen in the ratio of 1:2:1.