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1 question · 2021 · answers as per the UPSC key

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Which one of the following is a reason why astronomical distances are measured in light-years?

(a) Distances among stellar bodies do not change.
(b) Gravity of stellar bodies does not change.
(c) Light always travels in straight line.
(d) Speed of light is always same.
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Answer: (d) Speed of light is always same.