Correct Answer: Option 4 - Troposphere

Troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75 percent of the atmosphere's mass and 99 percent of its water vapor and aerosols. The lowest part of the troposphere, where friction with the Earth's surface influences air flow, is the planetary boundary layer. This layer is typically a few hundred meters to 2 km (1.2 mi) deep depending on the landform and time of day

Incorrect options

Stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler higher up and warmer farther down

Mesosphere is the layer of the Earth's atmosphere that is directly above the stratosphere and directly below the thermosphere. The mesosphere is located from about 50 km to 80-90 km altitude above the Earth's surface. Within this layer, temperature decreases with increasing altitude due to decreasing solar heating and increasing cooling by CO₂ radiative emission

Thermosphere is the layer of the earth's atmosphere directly above the mesosphere and directly below the exosphere. Within this layer, ultraviolet radiation causes ionization. The thermosphere begins about 90 km above the earth