When the prefix cyclo- comes before the name of a hydrocarbon, what does it mean?
a. the molecule is bent.
b. the molecule is linear.
c. the molecule is circular.
d. the molecule is branched.

When the prefix cyclo- comes before the name of a hydrocarbon, it means that the molecule is circular.

Explanation:

Hydrocarbons are organic compounds formed only by carbon and hydrogen atoms.

Hydrocarbons can be classified into aliphatic and aromatic. Aliphatic hydrocarbons are open chains, either linear or branched. Aromatic hydrocarbons have cyclic molecules, that is, the carbon atoms form a circle. In other words, they are defined as closed-chain hydrocarbons.

To name a cyclic hydrocarbon the prefix cyclo- is used to name an acyclic hydrocarbon. Then when the prefix cyclo- comes before the name of a hydrocarbon, it means that the molecule is circular.