For A.) and B.)

Diffusion of the electrons and holes from n and p side to p and n side, respectively, due to higher a concentration of holes on the p-side and lower at n-side and vice-versa for electrons results in systematic motion of charges take place.

Therefore, option A is incorrect and B is correct.

C.) Since, there are same number of electrons transferred as the number of holes transferred. Thus, the net charge transferred is zero.

Therefore, the option C is correct.

D.) As the During equilibrium there is no flow of charges at junction therefore the electric field there remains constant.

Therefore, the option D is correct.