A proton moving with a constant velocity passes through a region of space without any change in its velocity. If $\overrightarrow{\mathrm{E}}$ and $\overrightarrow{\mathrm{B}}$ represent the electric and magnetic fields respectively, then the region of space may have :

(A) $\mathrm{E}=0, \mathrm{~B}=0$

(B) $\mathrm{E}=0, \mathrm{~B} \neq 0$

(C) $\mathrm{E} \neq 0, \mathrm{~B}=0$

(D) $\mathrm{E} \neq 0, \mathrm{~B} \neq 0$

Choose the most appropriate answer from the options given below :