The correct order of molar heat capacities measured at 298 K and 1...

The molar heat capacity of Helium (a monatomic gas) at constant pressure is $C_p = \dfrac{5}{2}R \approx 20.8 \text{ J K}^{-1} \text{ mol}^{-1}$.

The molar heat capacity of Copper (a solid) follows the Dulong-Petit law, which gives $C_p \approx 3R \approx 24.9 \text{ J K}^{-1} \text{ mol}^{-1}$.

The molar heat capacity of Bromine (a diatomic liquid) is significantly higher due to translational, rotational, and vibrational degrees of freedom along with intermolecular interactions in the liquid state, having $C_p \approx 75.7 \text{ J K}^{-1} \text{ mol}^{-1}$.

Therefore, the correct order of molar heat capacities is Bromine(l) > Copper(s) > Helium(g).

Answer: Bromine(l) > Copper(s) > Helium(g)