Final answer:
The range of light hydrocarbons in heavier oils and bitumens is mostly C31 and above. Light hydrocarbons with smaller carbon chains are typically found in lighter oils and gases.
Step-by-step explanation:
The range of light hydrocarbons in heavier oils and bitumens is mostly C31 and above. These hydrocarbons have larger carbon chains, which contribute to their higher boiling points. Light hydrocarbons with smaller carbon chains, such as C5 to C10, are typically found in lighter oils and gases.