A body of mass $m$ falls from a height $R$ above the surface of the earth, where $R$ is the radius of the earth. What is the velocity attained by the body on reaching the ground? (Acceleration due to gravity on the surface of the earth is $g$)

  • A

    $gR$

  • B

    $\sqrt {gR} $

  • C

    $\sqrt {g/R} $

  • D

    $g/R$

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