Multiple choice By isomerisation of straight chain hydrocarbons, the octane number generally increase<font size="2">s</font> decrease<font size="2">s</font> remains constant cannot be d<font size="2">efined</font> Reveal answer Fill a bubble to check yourself A Correct answer Explanation Isomerisation converts straight-chain alkanes to branched isomers. Branched hydrocarbons have higher octane numbers because they resist knocking better in combustion engines.