Mercury boils at `367^(@)C`. However, mercury thermometers are made such that they can measure temperature up to `500^(@)C`. This is done by

Options

A. Maintaining vacuum above mercury column in the stem of the thermometer
B. Filling nitrogen gas at high pressure above the mercury column
C. Filling nitrogen gas at low pressure above the mercury level
D. Filling oxygen gas at high pressure above the mercury column

Answer

B

Explanation

By filling `N_2` gas at high pressure, the boiling point of mercury increases which extends the range up to `500^@ C`.