A, the "white gas" released from the beaker mouth is small water droplets formed by condensation of high-temperature water vapor released from the beaker, which belongs to liquefaction phenomenon, and this option is incorrect;

B, as can be seen from the image, when water boils, the temperature is constant, which is 96℃, so the boiling point of water at this time is 96℃, which is incorrect;

C, water in the process of boiling, constantly absorb heat, this option is correct;

D, the boiling point of water under standard pressure is 100℃, and the boiling point of water in this experiment is 96℃, so the pressure in the experiment is lower than the standard pressure, which is incorrect.

So choose C.