How does atmospheric pressure decrease with increase in temperature?
(A) Due to air expansion
(B) Due to decrease in density
(C) Both
(D) None

Hint:Use the concept that the high temperature heats the air molecule, and due to this, the air molecules gain kinetic energy. The high kinetic energy is responsible for the movement and expansion of the air molecules, and we know that pressure always decreases when the expansion of the air takes place.

Complete step by step answer:
The atmospheric pressure is that pressure, which is exerted by the air in the surrounding. The air is attracted to the earth due to the gravitational effect, so this attraction generates the force on the earth's unit area and is termed atmospheric pressure. We can measure the atmospheric pressure with the help of a barometer.
The variation in the atmospheric pressure occurs if temperature changes due to climatic effects. When the temperature rises, the particles of the air gain kinetic energy. So, due to the gain in kinetic energy, the air particles become excited and tend to move or expand from its position to another position. As a result of this expansion, the air particles' density decreases, and we know that if the air expansion occurs, then the pressure between the air particles decreases. So, the air expansion and decrease in density are responsible for the decrease in atmospheric pressure.
Therefore, due to air expansion and decrease in density, the atmospheric pressure decreases with an increase in temperature and the option (C) is correct.

Note:Remember the relation between temperature and pressure for the information about the atmospheric pressure variation. You can take help from the ideal gas equation. Because keeping one property like volume constant in an ideal gas, the relation of the other two properties like temperature and pressure, can be obtained.