Let the Charge Density in a Certain Region of Space $\rho$

Let the charge density in a certain region of space be $\rho$ . The electric field $\vec{E}$ in that region points in the $+x$ direction with $|\vec{E}|=$ constant. This implies

A) that $\rho$ is positive in that region.
B) that $\rho$ is negative in that region.
C) that $\rho$ is zero in that region.
D) that the field is physically impossible.
E) nothing useful about the region's charge density.