Which among the following is used in the treatment of cancer?

Which among the following pairs of compounds is not isomorphous?

Which among the following compounds is used as selective weed killer?

Calculate the difference between heat of combustion of carbon monoxide gas at constant pressure and at constant volume at $27^{\circ} \mathrm{C} ?\left(R=2 \mathrm{cal} \mathrm{K}^{-1} \mathrm{~mol}^{-1}\right)$