A Radio Galaxy Is Any Galaxy That

A radio galaxy is any galaxy that:

A) has two lobes, one on each side of the galaxy, which emit synchrotron radiation at radio wavelengths.
B) emits large amounts of energy from the whole galaxy at radio wavelengths.
C) is invisible at optical wavelengths (ordinary light) and detected only at radio wavelengths.
D) has a bright, compact nucleus that emits large amounts of thermal energy at radio wavelengths.