The line $lx + my + n = 0$ will be a tangent to the circle $x^2 + y^2 = a^2$ if

  • A
    $n^2(l^2 + m^2) = a^2$
  • B
    $a^2(l^2 + m^2) = n^2$
  • C
    $n(l + m) = a$
  • D
    $a(l + m) = n$

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