A compound X, $\mathrm{C}{}_4\mathrm{H}{}_{10}\mathrm{O}{}_2$, is optically inactive and cannot be resolved. It consumes one mole of $\mathrm{HIO}{}_4$ per mole and gives a single organic product only. X is

One mole of $\mathrm{HIO}{}_4$ shows a vicinal diol. A single product means the two halves are identical, which rules out butane-1,2-diol (methanal plus propanal) and 2-methylpropane-1,2-diol (methanal plus propanone). Butane-2,3-diol gives only ethanal, and the inactive, non-resolvable stereoisomer is the meso form (the (2R,3R) form is optically active).