Kindle is related to burn in the same way angry is related to

Preface to Book as Overture is to......

Choose the correct alternative for the given relation.

Earth : Sun : : Moon : ?

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Smile : Laugh : Cry

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$6 : 18 :\, : 4 : \,?$

Choose the correct alternative for the word belongs to the same group.

Which of the following is the same as Wrestling, Karate, Boxing ?