Answer:
Troposphere
Explanation:
Troposphere is the lowest level in this list which only rises a little over 10 kilometers high.
The next on the list is the Stratosphere which lays on top of the Troposphere and it is about 40 kilometers thick
On top of the Stratosphere is the mesosphere which is about 35 kilometers thick
As for the Ionosphere, it lays on top of the Thermosphere which is a layer above the Mesosphere
Here is a visual if you need it
