Why is it advised to use a telescope in the clear sky?
(A) Less interference between telescope and object
(B) To get better quality of image
(C) To reduce the lateral shift in images caused by the environment
(D) All of the above

Hint: It is recommended to use a telescope in clear sky. Objects placed at large distances are viewed objects using telescopes. Since the objects are very far there are many disturbing agents that can affect the observations like dust, atmosphere, clouds glares from nearby light sources etc. Clear sky reduces the unwanted effects due to all of these agents.

Complete step by step answer:
Telescope: It is an optical instrument which is used to view distant objects.
Atmospheric Interference: Radiations from the particles present in air and sun’s rays leads to atmospheric interference. These radiations are absorbed by the earth’s surface leading to greenhouse effect.
When the sky is clear, there will be less interference because unwanted particles present in the air will reduce.
Good quality images are obtained kept far away from the earth. In order to reach an infinitely placed object, it would be effective if there is less obstacle in the path. This ensures good quality images.
Lateral shift: Perpendicular distance between incident ray and emergent ray. This perpendicular distance is regarded as lateral shift. Having a high density of the medium means longer path length. This means that the lateral shift increases. Smaller distractions reduce the lateral shift.

Since options A, B and C are correct. Since all options are correct therefore option D is correct.

Note:
 A lot of difficult looking words like lateral shifts etc can be intimidating. So, one should use tricks. Clearly the first option and the second options look valid. Since there are less objects/ distractions there will be less interference. And having less dust means that the object can be seen clearly. The only option allowing us to choose both of these options is the last option-Option D.