The direction cosines of z-axis are :

1, 0, 0 0, 1, 0 0, 0, 1 1, 1, 1

0, 0, 1

The correct answer is Option (3) → 0, 0, 1 z axis is represented by a point on it as $\vec v=0\hat i+0\hat j+z\hat k$ $|\vec v|=|z|=z$ so D.C. = $\frac{0}{z},\frac{0}{z},\frac{z}{z}=0,0,1$