The rubber used to make petrochemicals tank lining is:

The correct answer is Option (4) → Buna-N

Buna-N is a copolymer of 1,3-butadiene and acrylonitrile:

    nCH₂=CH–CH=CH₂ + nCH₂=CH–CN → [–\( \ce{CH2-CH=CH-CH2-CH2-CH(CN)} \)–]_n (copolymerisation)

The polar CN groups make it resistant to the action of petrol, lubricating oil and organic solvents, so it is used for oil seals and tank lining.

Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.

NCERT (Pre-rationalised edition, 2022-23):
Synthetic Rubbers – “… Buna –N is obtained by the copolymerisation of 1, 3 – butadiene and acrylonitrile in the presence of a peroxide catalyst. It is resistant to the action of petrol, lubricating oil and organic solvents. It is used in making oil seals, tank lining, etc.”