The linear mapping x > Ux preserves lengths and orthogonality. Which of the following equalities is/are true about this statement? I. (UX){Uy)=x.y
II. (Ux).(Uy)=x.y
III. (Ux).(Uy)=0x.y=0
(a) I only
(b) II and III only
(c) I and II only
(d) I and III only