Correct Answer:
A. 100°C
The boiling point of water at sea level is 100°C (212°F). This is a fundamental physical property, defined as the temperature at which water's vapor pressure equals the standard atmospheric pressure at sea level, allowing it to transition from liquid to gas.
- 90°C and 80°C are below the standard boiling point and would not cause water to boil at sea level.
- 120°C is above the standard boiling point; water would already be steam at this temperature under normal atmospheric pressure. The boiling point can change with pressure, but 100°C is the standard reference.