Let $P = (x_1, y_1, z_1)$ and $Q = (x_2, y_2, z_2)$ be two points. If the direction cosines of a line $AB$ are $l, m, n$,then the projection of the line segment $PQ$ on the line $AB$ is:

  • A
    $\left[ \frac{1}{l}(x_2 - x_1) + \frac{1}{m}(y_2 - y_1) + \frac{1}{n}(z_2 - z_1) \right]$
  • B
    $\left[ l(x_2 - x_1) + m(y_2 - y_1) + n(z_2 - z_1) \right]$
  • C
    $\left| \frac{1}{lmn} \left[ l(x_2 - x_1) + m(y_2 - y_1) + n(z_2 - z_1) \right] \right|$
  • D
    None of these

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