Read the two statements and choose the correct option.

I. A line has infinitely many sets of direction ratios but only two sets of direction cosines.

II. If $l, m, n$ are direction cosines, then $l + m + n = 1$.

Explanation

1. 01

   I: any non-zero multiple of the ratios is again a set of ratios; the cosines are fixed up to the sign of the direction. True.

2. 02

   II: it is $l^{2} + m^{2} + n^{2} = 1$; for the $x$-axis reversed, $-1 + 0 + 0 \ne 1$. False.