A carbon atom can bond to four other atoms because it has

a. four different cations.

c. two inner energy levels.

b. four valence electrons.

d. no protons in its nucleus.

Option C is correct.

Explanation:

A carbon atom can bond to four other atoms because it has four valance electrons. To fill these four valance electrons the carbon atom have to bond with other four atoms. The bond forms by carbon atom are the covalent bonds. These covalent bonds are the chemical bonds.

The simple example of carbon covalent bond is methane. In the methane a carbon atom bonds with four hydrogen atoms. these bonds are the chamical bonds namely covalent or chemical bonds.

Thus option C is correct.