Select the option that is related to the third word in the same way as the second word is related to the first word.
Planet : Earth :: Celestial object : ?

Correct option is C

​$$\text{Given analogy: } \text{Planet : Earth} :: \text{Celestial object : ?} \\[6pt]\text{Planet is a type of Earth.} \\[6pt]\text{A Celestial object refers to any natural object outside Earth's atmosphere, such as stars, planets, comets, etc.} \\[6pt]\text{Since Earth is a planet, the celestial object most closely related is a Star.} \\[6pt]\Rightarrow \text{Celestial object : Star} \\[6pt]\text{Hence, the correct answer is } \boxed{\text{Star}}.$$​​