A vector $A$ has components $A_{1}, A_{2}, A_{3}$ in a right-handed rectangular cartesian coordinate system $O x, O y, O z$. The coordinate system is rotated about the z-axis through an angle $\frac{\pi}{2} .$ The components of $A$ in the new coordinate system are
(A) $A_{1},-A_{2}, A_{3}$
(B) $A_{2}, A_{1}, A_{3}$
(C) $A_{1}, A_{2},-A_{3}$
(D) $A_{2},-A_{1}, A_{3}$.