A cubical region of space is filled with some uniform electric and magnetic fields. An electron enters the cube across one of its faces with velocity $\overline{V}$  and a positron enters via opposite face with velocity $-\overline{V}$  simultaneously. At this instant,

a) the electric forces on both the particles cause identical accelerations

b) the magnetic forces on both the particles cause equal accelerations.

c) both particles gain or loose kinetic energy at the same rate.

d) the motion of the centre of mass $\left(CM\right)$  is determined by $\overline{{\displaystyle B}}$  alone.

Which of the statement is wrong: