Which class includes an unsaturated hydrocarbon with a ring structure?

The correct answer is aromatic hydrocarbons.

Explanation:

Aromatic compounds are named on the basis of their fragrant characteristics and are unsaturated hydrocarbon ring compositions, which demonstrate unique characteristics, comprising unusual stability because of their aromaticity.  

They are usually signified as resonance compositions comprising double and single bonds. However, the bonding is more robust in comparison to a conjugated structure, and it is more precisely signified as delocalized electron density shared among all the atoms in the ring.  

adding or remove a gaseous reactant or product changes the concentrations. if the concentration of reactant or product is increased, the system will shift away from the side in which concentration was increased (i.e. if the concentration of reactants is increased, the system will shift toward the products. if more products are added, the system will shift to form more reactants). conversely, if the concentration of reactant or product is decreased, the system will shift toward the side in which concentration was decreased (i.e. if reactants are removed, the system will shift to form more reactants. if the concentration of products is decreased, the equilibrium will shift toward the products).

explanation: