Concept:A barometer measures atmospheric pressure through the height of a mercury column supported by the air.
Explanation:At normal atmospheric pressure, the air pressure balances the weight of the mercury column.
At sea level, this balance occurs when the mercury column is exactly
76 cm high.
Equivalently, this is
760 mm of mercury, which is standard pressure.
It is measured at
0∘C to avoid expansion effects of mercury.
Among the given options, only
76 cm matches the standard sea-level value.
Answer:D.
76 cm at sea level.