If the direction cosines $l, m, n$ of two lines are satisfying the relations $l+m+n=0$, $l m=0$, then the angle between those two lines is

• A

  $0$
• B

  $\frac{\pi}{2}$
• C

  $\frac{\pi}{4}$
• Correct answer
  D

  $\frac{\pi}{3}$

Hence, the correct answer is option: 'D'.