Two identical balls having like charges and placed at a certain distance apart repel each other with a certain force. They are brought in contact and then moved apart to a distance equal to half their initial separation. The force of repulsion between them increases $4.5$ times in comparison with the initial value. The ratio of the initial charges of the balls is

  • A

    $2$

  • B

    $3$

  • C

    $4$

  • D

    $6$

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  • [KVPY 2018]