Solution

Why does the water level rise inside the glass, once the flame extinguishes?

a) The entire air inside of the glass is burnt by the candle. Once the candle extinguishes, no air but only a vacuum is left inside of the glass. This vacuum sucks the water into the glass.

b) The candle burns paraffin. Thus, the candle gets lighter and swims. Therefore, it displaces less water than before and the water level rises.

c) Once the flame extinguishes, the capillary-effect takes place which make the water in tubes rise.

d) The flame of the candle heats up the air. After the flame extinguishes the air cools down and the air-pressure inside of the glass decreases. The water is now pressed inside of the glass due to the higher air-pressure outside of the glass.