42. which of the following is an example of a first order phase transition ? (a) a liquid-gas phase transition at the critical point (b) a liquid-gas phase tran

42. Which of the following is an example of a first order phase transition ? (A) A liquid-gas phase transition at the critical point (B) A liquid-gas phase transition away from the critical point (C) A normal metal-super conductor transition (D) Normal liquid Helium to super fluid helium transition