(N/A) Alkanes are generally inert towards common oxidizing agents like $KMnO_4$ or $K_2Cr_2O_7$ at room temperature because they lack functional groups and have strong $C-C$ and $C-H$ sigma bonds.
However,alkanes undergo combustion,which is a highly exothermic oxidation reaction.
For example,in the combustion of butane $(C_4H_{10})$: $2C_4H_{10} + 13O_2 \rightarrow 8CO_2 + 10H_2O$.
In $C_4H_{10}$,the oxidation state of carbon is $-2.5$,while in $CO_2$,it is $+4$. Since the oxidation number of carbon increases,this process is an oxidation reaction.
Therefore,the statement implies that alkanes are resistant to mild oxidation but undergo vigorous oxidation (combustion) at high temperatures.