Final answer:
Mercury (Hg) is the element that would be in a liquid state at 758 K and standard pressure.
Step-by-step explanation:
The element that is a liquid at 758 K and standard pressure is mercury (Hg). Mercury is known to be one such metal that is in liquid state at room temperature. Given its melting point, at a temperature of 758 K, which is significantly higher than room temperature, mercury would still be in a liquid state under standard pressure conditions. Other elements listed, such as oxygen (O), hydrogen (H), and nitrogen (N), would be in a gaseous state at these temperatures under standard pressure conditions.