Indicate whether each statement is true or false: 

(a) The critical pressure of a substance is the pressure at which it turns into a solid at room temperature. 

(b) The critical temperature of a substance is the highest temperature at which the liquid phase can form. 

(c) Generally speaking, the higher the critical temperature of a substance, the lower its critical pressure. 

(d) In general, the more intermolecular forces there are in a substance, the higher its critical temperature and pressure.