Seyfert Galaxies Are a Distinct Class of Galaxies Because They

Seyfert galaxies are a distinct class of galaxies because they

A) are very close to the Milky Way and appear to be gravitationally bound to it.
B) have very bright, very hot starlike central cores with variable energy output.
C) are completely devoid of structure, appearing to be amorphous spheres of gas and dust.
D) are in the constellation of Seyfert in Earth's southern hemisphere sky.