An alkyne on treatment with cold alkaline $KMnO_4$ gives $2-­oxo$ propanal. Alkyne is

Question

$\begin{array}{1 1}a)\; CH_3C\equiv CH\\b)\; CH_3-C\equiv C-CH_3\\c)\; HC\equiv C- CH_2-CH_3\\d)\;HC\equiv CH\end{array}$