The correct answer is b. Negative linear relationship. The graph shows a clear negative trend, meaning that as the altitude increases, the temperature decreases. This is a common relationship in the troposphere, the lowest layer of the Earth's atmosphere. The temperature in the troposphere generally decreases by about 6.5°C (12°F) for every 1000 meters (3,280 feet) of altitude.
Here are some of the reasons why the temperature decreases with altitude in the troposphere:
Adiabatic lapse rate: As air rises, it expands and cools. This is because the pressure on the air decreases as it rises, and the air has to do work to expand against the decreasing pressure. The rate at which air cools as it rises is called the adiabatic lapse rate.
Greenhouse gases: Greenhouse gases, such as water vapor and carbon dioxide, trap heat from the sun. The concentration of greenhouse gases decreases with altitude, so there is less heat to trap in the upper atmosphere.
Solar radiation: The sun's rays heat the ground and the lower atmosphere. However, as the altitude increases, the air becomes more transparent to solar radiation, so less heat is absorbed.
The graph shows a negative linear relationship between temperature and altitude, which is consistent with the general trend in the troposphere.