Which compound is used for increase of octane rating?

Correct answer: (c) Tetraethyllead

Explanation

Octane rating measures a fuel's resistance to engine knocking (premature ignition); higher values give smoother, more efficient combustion.

Tetraethyllead (TEL) was added to petrol as an anti-knock agent to raise the octane number, though it is now phased out for being toxic.

The other compounds are not used as octane boosters.