When can water remain a liquid above 100^circ C H_(2)O must be completely in the gas phase. Pressure must be greater than 760 mm Hg. Water cannot be heated above 100^circ C Pressure must be less than sea level.

Water can remain a liquid above if the pressure is greater than 760 mm Hg. At standard atmospheric pressure (760 mm Hg), water boils at . However, if the pressure is increased, the boiling point of water also increases, allowing it to remain in the liquid state at temperatures above . Therefore, the correct answer is:Pressure must be greater than 760 mm Hg.