8. The circle $\rho=D \cos \theta+E \sin \theta$ is tangent to the line of the polar axis if and only if ( ).
A. $D \cdot E=0$
B. $D \cdot E \neq 0$
C. $D=0, E \neq 0$
D. $D \neq 0, E=0$
8. From $\rho=D \cos \theta+E \sin \theta$ to the Cartesian equation is $\left(x-\frac{D}{2}\right)^{2}+\left(y-\frac{E}{2}\right)^{2}=\frac{1}{4}\left(D^{2}+E^{2}\right)$, or from $\rho=$ $E \sin \theta(E \neq 0)$ representing a circle tangent to the line of the polar axis, it is known that the answer is $\mathrm{C}$.