9. The points A(2, -1, 0), B(1, 1, 1), C(3, 0, 1) and $D\left(-\frac{1}{2}, \frac{1}{2}, \frac{1}{\sqrt{2}}\right)$ are given. Which of the following statements are true?
I. $|\vec{AB}| > |\vec{BC}|$
II. The position vector of A is parallel to the vector $\vec{u} = -2\vec{i} + \vec{j}$.
III. The position vector of D is a unit vector.
(a) I only
(b) II only
(c) I, II
(d) II, III
(e) I, II, III