The correct answer is B. Lapse rate.
The lapse rate is the rate at which temperature decreases with increasing altitude. It is typically expressed in degrees Celsius per kilometer (°C/km). The lapse rate is not constant, but varies with altitude and location. In the troposphere, the lowest layer of the atmosphere, the lapse rate is typically about 6.5°C/km. This means that for every kilometer you go up in altitude, the temperature decreases by about 6.5°C.
The lapse rate is important because it affects the weather. A high lapse rate means that the atmosphere is stable, and there is little mixing of air. This can lead to clear skies and calm winds. A low lapse rate means that the atmosphere is unstable, and there is more mixing of air. This can lead to clouds, rain, and thunderstorms.
The lapse rate is also important for aviation. Pilots need to be aware of the lapse rate so that they can plan their flights accordingly. A high lapse rate can cause aircraft to lose altitude rapidly, while a low lapse rate can cause aircraft to gain altitude rapidly.
A. Temperature slope is not a correct answer because it is not a technical term used in meteorology.
B. Lapse rate is the correct answer because it is the rate at which temperature decreases with increasing altitude.
C. Sounding is not a correct answer because it is a technique used to measure the temperature and pressure of the atmosphere.
D. Thermocline is not a correct answer because it is a layer of the ocean where the temperature changes rapidly with depth.