Answer: True
Step-by-step explanation:
Petroleum and natural gas are both fossil fuels. They contain a mixture of hydrocarbons but they commonly have alkanes as their composition. The petroleum and natural gas produce after the degradation and decomposition of the organic matter generated after the dead and decaying plant and animal matter under the heap of sediments for long years. The natural gas specifically have methane, butane and propane. Therefore, on the basis of the above description, this can be said that natural gas and petroleum are mostly alkanes.