A mixture of methanol vapour and air is passed over heated copper. The products are

A mixture of methanol vapour and air is passed over heated copper. The products are formaldehyde and hydrogen.

Methanol is oxidised to produce formaldehyde and hydrogen in the presence of copper and air.

${\mathrm{CH}}_3\mathrm{OH}\underset{\mathrm{Cu}}{\stackrel{\text{ air }}{⟶}}\mathrm{HCHO}+{\mathrm{H}}_2$

Hence option B is correct