The coordinates of $P \equiv(1, 2, 3)$ and $O \equiv(0, 0, 0)$ are given. Find the direction cosines of $\overline{OP}$.

The direction cosines of the line which bisects the angle between the positive direction of $Y$ and $Z$ axes are

The angle between the straight lines,whose direction cosines are given by the equations $2l + 2m - n = 0$ and $mn + nl + lm = 0$,is:

The direction cosines of the line passing through $P(2, 3, -1)$ and the origin are

The number of straight lines that are equally inclined to the three-dimensional coordinate axes is

$\text{Assertion (A)}$: The direction ratios of line $L_1$ are $2, 5, 7$ and those of line $L_2$ are $\frac{4}{\sqrt{19}}, \frac{10}{\sqrt{19}}, \frac{14}{\sqrt{19}}$. The lines $L_1, L_2$ are parallel.
$\text{Reason (R)}$: The direction ratios of a line $L_1$ are $a_1, b_1, c_1$ and those of another line $L_2$ are $a_2, b_2, c_2$. The lines $L_1$ and $L_2$ are parallel if $a_1 a_2+b_1 b_2+c_1 c_2=0$.
The correct option among the following is