Express the complex number $z=2-4i$ in the polar form.

• A. $z=2\sqrt5\left(\sin297\degree+i\cos297\degree\right)$
• B. $z=2\sqrt5\left(\sin63\degree+i\cos63\degree\right)$
• C. $z=2\sqrt5\left(\cos297\degree+i\sin297\degree\right)$
• D. $z=2\sqrt5\left(\cos63\degree-i\sin63\degree\right)$