Concept:Arrange sentences in logical order so the paragraph flows smoothly from S1 to S6.
Explanation:S1 introduces the sun as Earth's main energy source.
P describes how the sun's rays travel in different wavelengths (ultraviolet, visible, infrared).
S defines the term "insolation" — radiant energy from the sun that reaches Earth.
Q explains what happens when insolation reaches Earth — it is partly absorbed and turned into heat.
R mentions that energy from other celestial bodies is very small compared to the sun.
S6 says only a small part of insolation is absorbed and converted to thermal energy.
Thus the correct order after S1 is P → S → Q → R, which matches option A (PSQR).
Answer:Option A. PSQR