Answer:
Options (2), (3) and (6)
Explanation:
Air pressure is usually defined as the weight that the atmosphere exerts downward on the earth's surface. This air pressure varies with the changes that occur in terms of height or altitude. The value of air pressure increases towards the mean sea level and decreases as the height increases.
This atmospheric pressure is commonly measured by an instrument which is known as a barometer. It helps in the weather forecasting.
The S.I unit of atmospheric pressure is Pascal (Pa). In the C.G.S system, the units used are millimeter (mm) of mercury and millibar (mb).
Thus, the correct answers are options (2), (3) and (6).
