Question

Ionosphere extends from about $80 - 1000{\text{ }}km$ :
(A)Above the earth’s surface
(B)Above the sea’s surface
(C)Below the sea’s surface
(D)None of the above.

Answer 1

Hint
We will take into account the origin of measurement for the layers of atmosphere. Then we will try to refer to the analogy for this problem as well.

Complete step by step answer
Atmosphere is the envelope of air surrounding and covering the earth surface. Its benefits include protecting earthly beings from harmful UV rays of the sun and other heavenly bodies.
There are mainly $6$ layers of the earth’s atmosphere. They are namely in order:
(i) Troposphere
(ii) Stratosphere
(iii) Mesosphere
(iv) Thermosphere
(v) Ionosphere
(vi) Exosphere
The work of the troposphere is to make earth suitable for inhibiting. It provides needful oxygen for us to breathe. It extends in a range of $8 - 14.5km$ from the earth’s surface.
Then comes the stratosphere where we can find the ozone layer. The function of the ozone layer is to protect us from harmful UV rays of the heavenly bodies like the sun and other stars. It extends in a range of $14.5 - 50km$ from the earth’s surface.
Then again comes the mesosphere. It is the layer responsible to burn most of the meteors and asteroids before they can reach the earth surface. It extends in the range of $50 - 85km$ from the earth’s surface.
Then comes the thermosphere. It is the layer of the atmosphere just before we get to outer space. This layer is responsible for making space exploration and communication possible for us. It extends in a range of $85 - 600km$ from the earth’s surface.
Then comes the Ionosphere which starts between the extent of the mesosphere piercing through the extent of the thermosphere. It is the layer of the atmosphere which contains particles ionized due to the direct effect of UV radiations from the sun and other stars. It extends in a range of $80 - 1000km$ from the earth surface.
Finally comes the exosphere. It is the layer of the atmosphere which acts as a transition interface from a region under the influence of gravity to a region without. It extends in a range of $1000 - 19000km$.
Hence, the correct option is (A).

Note
All these values are based on observations. Though they are very precise to the original value.