We Interpret the Presence of More AGNs in the Past

We interpret the presence of more AGNs in the past than today to indicate that

A) there were fewer galaxy-galaxy interactions in the past.
B) there were more galaxy-galaxy interactions in the past.
C) supermassive black holes were larger in the past.
D) today's AGNs are hidden primarily by large amounts of cold gas and dust.
E) AGNs had bigger central black holes in the past.