Express the complex number $z=1-\frac{\sqrt{3}}{3}i$ in polar form.

• A. $z=\frac{2\sqrt{3}}{3}(\cos \frac{\pi }{6}-i\sin \frac{\pi }{6})$
• B. $z=\frac{2\sqrt{3}}{3}(\cos \frac{13\pi }{6}+i\sin \frac{13\pi }{6})$
• C. $z=\frac{2}{\sqrt{3}}(\cos \frac{11\pi }{6}+i\sin \frac{11\pi }{6})$
• D. $z=\frac{2\sqrt{3}}{3}(\cos \frac{11\pi }{6}+i\sin \frac{11\pi }{6})$