In an experiment, one of the open ends of a glass tube is in a dish filled with mercury while the other end is closed by a stopcock. The distance between the surface of the mercury to the stopcock is 900 mm. At 20 ºC, the height of mercury in the tube is equal to the height of mercury in the dish.

Which image corresponds to the level of mercury in the tube when the temperature is lowered to –50 ºC?