Which of the following is not a constituent of petroleum?

Petroleum is a naturally occurring fossil fuel, and refineries separate it into a range of distinct fractions through fractional distillation based on differing boiling points; every genuine fraction obtained this way counts as a constituent of petroleum. Coke, by contrast, is a solid carbon fuel obtained by heating coal (not petroleum) in the absence of air — a process called destructive distillation or carbonisation.

Checking each option against this distinction shows that petrol, lubricating oil, and paraffin wax are all fractions obtained directly from refining crude petroleum, while coke traces back to coal rather than petroleum.

• Petrol — a light, highly volatile fraction distilled from crude petroleum and used as motor fuel.

• Lubricating oil — a heavier, high-boiling fraction distilled from crude petroleum, used to reduce friction in machinery.

• Paraffin wax — a solid fraction distilled from crude petroleum, used in candles and waterproofing.

• Coke — produced by carbonising coal, not by refining petroleum.

Since three of the four options are obtained directly from petroleum refining and only one traces back to coal, that one is the correct answer to which item is not a constituent of petroleum.