Which is a characteristic of aromatic hydrocarbons? A. Alternating single and double bonds
B. Bonds between oxygen and carbon atoms
C. Oxygen atoms bonded to hydrogen atoms
D. Two hydrogen atoms bonded together​

A. Alternating single and double bonds

Explanation:

Hydrocarbons i.e. hydrogen and carbon containing compounds, are grouped into two namely: aliphatic and aromatic hydrocarbons. Aliphatic hydrocarbons contains straight or branched chains of carbon and hydrogen atoms in their structure e.g. alkanes, alkenes etc.

On the other hand, aromatic hydrocarbons are cyclic hydrocarbons containing one or more cyclic rings. The benzene ring is the basis of all aromatic hydrocarbons and one characteristics of benzene is that it possesses an alternating single (-) and double bonds (=) in their structure.

Since benzene is a building constituent of aromatic hydrocarbons, an "alternating single and double bond" is a characteristics of aromatic hydrocarbons.