The correct answer is option 2, Exosphere. The exosphere is the outermost layer of the Earth`s atmosphere, located farthest from the Earth`s surface. It extends from about 500 kilometers (310 miles) above the surface to the edge of space, approximately 10,000 kilometers (6,200 miles).
Option 1, the Stratosphere, is the second layer of the Earth`s atmosphere. It is located above the troposphere and contains the ozone layer, which plays a crucial role in protecting the Earth from harmful ultraviolet radiation.
Option 3, the Ionosphere, is a region within the Earth`s atmosphere that is ionized by solar radiation. It is located between the mesosphere and exosphere.
Option 4, the Mesosphere, is the layer of the Earth`s atmosphere located above the stratosphere and below the thermosphere. It is the coldest layer and is where meteors typically burn up upon entry into the Earth`s atmosphere.
Therefore, option 2, Exosphere, is the correct answer.