The octane number has zero value for:
A.Iso-octane
B.n-octane
C.n-heptane
D.tetraethyl lead

Hint: Octane number is defined as the presence of iso-octane by volume in a mixture of isooctane and n-heptane. Octane number is the measure of resistance towards auto-ignition of an engine fuel.

Complete step by step answer:
Octane number is the measure of resistance towards auto-ignition of an engine fuel. It is a scale from zero to 100. Basically octane number is defined for the mixture of n-heptane and iso-octane in terms of volume of iso-octane present in the mixture. If there is pure n-heptane then its octane number is 0. If only pure iso-octane is there then its octane number is 100. The value of octane number for the mixture of n-heptane and iso-octane lies in between zero to 100.

So, the correct option is option C.
Additional information:
The ignition of fuel in the mixture cylinder causes sound during combustion causes a pinging sound known as knocking. The shock waves generate in the engine because of heating continuously over the same space. This leads to self ignition. This continuous knocking decreased the efficiency of the engine. This leads to increased risk of engine damage. The aromatic or branched hydrocarbons are preferred at higher temperature because they are less prone to self ignition. The anti knocking additives can be added to increase the octane rating of the engine.

Note:
The octane number can be measured by two types that are MON and RON. MON is the motor octane number. It is the octane number that is measured at 900 rpm or revolution per minute. RON is the research octane number is the octane number that is measured at 600 revolutions per minute.