A proton, moving with velocity v,enters a region of uniform vector E & B such that vector v, E & B are mutually perpendicular the proton is deflected along positive x - axis when either of the fields or both are switched on simultaneously. Which of the following supports the argument given above?
(a) vector B may be along negative y- axis
(b) vector B may be along positive z - axis
(c) vector E is along positive x- axis
(d) v may be along positive y- axis
