$A$ person cannot see objects beyond $3 \, m$. What should be the focal length of the lens required to see objects at $12 \, m$?

  • A
    $-3/4 \, D$
  • B
    $3 \, D$
  • C
    $-1/4 \, D$
  • D
    $-4 \, D$

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