Concept:Cracking breaks larger hydrocarbon molecules into smaller, more useful products, including alkenes.
Explanation:Alkenes are unsaturated hydrocarbons that contain at least one carbon-carbon double bond.
They are not produced by combustion of alkanes, polymerisation, or hydrogenation of vegetable oils.
In the cracking process, long-chain hydrocarbons are heated, often with a catalyst, to break large molecules into smaller ones.
This process commonly yields a mixture of alkanes and alkenes.
Therefore, cracking is the key industrial method used to manufacture alkenes.
Answer:B. the cracking of hydrocarbons.