Which of the atmosphere's four main layers contains both the ionosphere and exosphere?

The atmosphere's four main layers include the troposphere, stratosphere, mesosphere, and thermosphere. The ionosphere is a part of the thermosphere, where ionization occurs due to solar radiation. The exosphere, which is the outermost layer of the atmosphere, is also considered part of the thermosphere, as it gradually transitions into outer space. Thus, both the ionosphere and exosphere are found within the thermosphere.