Tetraethyl lead (TEL) in petrol was used as antiknocking agent, which creates lead pollution. In order to avoid lead pollution, the substitute of TEL is used in unleaded-petrol. The substitute is denoted as:
Correct option is A. $$AK-33-X$$
The substitute of TEL which is used in unleaded petrol is cyclopentadienyl manganese tricarbonyl also known as $$\mathrm{AK-33-X}$$.
Hence, Option "A" is the correct answer.