If the direction cosines of a line are $\frac{1}{c},\frac{1}{c}, \frac{1}{c},$ then

$0 < c < 1 $ $ c > 2 $ $ c < 2 $ $c = ± \sqrt{3}$

$c = ± \sqrt{3}$

If $\frac{1}{c},\frac{1}{c}, \frac{1}{c}$ are the direction cosines of a line, then $\frac{1}{c^2}+\frac{1}{c^2}+\frac{1}{c}=1 ⇒ c =± \sqrt{3} $