In a region having a uniform field vector B = B0j , a proton is fired from origin with velocity v = v0j + v0k. The subsequent motion of the proton has the best description give by the following statement(s).
(a) Its x and z co-ordinates cannot be zero at the same time
(b) If y co-ordinate will be proportional to its time of flight
(c) Its x co-ordinates can never be negative
(d) Its x co- ordinate can never be positive