Which fossil fuel is a mixture of aromatic hydrocarbons with high molar masses?

Coal

Explanation:

The hydrocarbons that are in liquid and gaseous form have low molar masses when compared to the solids. Solid form of aromatic hydrocarbon with high molar mass is Coal, which serves as a fossil fuel.

Fossil fuels are the fuels that are also called as non renewable sources of energy. Non renewable sources of energy get depleted over a period of usage.

Renewable sources are the sources like the solar energy, wind energy and the likes.

Coal ...