The magnetic moment of a diamagnetic atom is 

• much greater than one

• one

• equal to zero

• equal to zero

D.

equal to zero

Atoms which have paired electrons have the magnetic moment zero. Because diamagnetism is the intrinsic property of every material and it is generated due to the mutual interaction between the applied magnetic field and orbital motion of electrons.
so, the magnetic moment of a diamagnetic atom is equal to zero.