13. The quality of petrol as an engine fuel improves with a higher amount
of
A. branched chain alkanes.
B. branched chain alkenes.
C. branched chain alkynes.
D. straight chain alkynes.
E. straight chain alkynes.

The correct option is;

A. Branched chain alkanes

Explanation:

By the process of cracking of petroleum, higher quality petrol are formed by converting straight chain petrol to branched petrol, which are the grade of petrol that burns more smoothly and therefore efficiently within internal combustion engines

The cracking process includes;

a) The conversion of alkanes which are large molecules into branched octanes

b) The conversion of alkanes with straight chain into branched chain alkanes

c) The formation of a branched chain alkane and an alkene from straight chain alkanes

d) The formation of branched chain alkane and hydrogen gas from a straight chain alkane.

catya your not at all which answer i've seen you do this on another question!