If the magnetic dipole of moment of an atom of diamagnetic material, paramagnetic material and ferromagnetic material are donated by `mu_d, mu_p` and `mu_f` respectively, then:
A. `mu_(d) ne 0` and `mu_(f) ne 0`
B. `mu_(p) = 0` and `mu_(f) ne 0`
C. `mu_(d) = 0` and `mu_(p) ne 0`
D. `mu_ ne 0` and `mu_(p)=0`