Which one of the following is the first layer of the atmosphere?

The correct answer is Option (4) → Troposphere

The troposphere is the lowest layer of the atmosphere, the one next to the Earth’s surface. It reaches about 8 km at the poles and about 18 km at the equator, and it holds almost all the water vapour, clouds and weather. In it, temperature falls with height.

Going up from the surface, the layers are troposphere, stratosphere (with the ozone layer), mesosphere, thermosphere and exosphere.