Law of corresponding states says that

A. Two different gases behave similarly, if their reduced properties (i.e. P, V and T) are same

B. The surface of separation (i. e. the meniscus) between liquid and vapour phase disappears at the critical temperature

C. No gas can be liquefied above the critical temperature, howsoever high the pressure may be.

D. The molar heat of energy of gas at constant volume should be nearly constant (about 3 calories)