6. (2000 National College Entrance Exam) In the complex plane, the vector corresponding to the complex number $3-\sqrt{3} \mathrm{i}$ is rotated clockwise by $\frac{\pi}{3}$. The complex number corresponding to the resulting vector is ().
A. $\sqrt{3}-3 \mathrm{i}$
B. $-2 \sqrt{3} \mathrm{i}$
C. $2 \sqrt{3} \mathrm{i}$
D. $3+\sqrt{3} \mathrm{i}$
6. B. Reason: Since $\arg (3-\sqrt{3} \mathrm{i})=\frac{11}{6} \pi$, let $z=3-\sqrt{3} \mathrm{i}$, then $\angle X O Z=\frac{\pi}{6}$.

When the vector $\overrightarrow{O Z}$ is rotated clockwise by $\frac{\pi}{3}$, the resulting vector aligns with the negative direction of the imaginary axis, hence the answer is B.