Alkanes containing 6 or more carbon atoms catalytically treated under pressure, passed over chromic oxide carried on an alumina support at temperature ranging 480-550 degree C,eventually

Question

$\begin{array}{1 1}a)\;Increases\; knocking\; efficiency \;of \;fuel\\b)\; Decreases\; knocking\; efficiency \;of\; fuel\\c)\; Knocking\; remains \;unaffected\\d)\; Can't \;be\; predicted\end{array}$