How Do We Know What Happens at the Event Horizon

Multiple Choice

How do we know what happens at the event horizon of a black hole?

A) Physicists have created miniature black holes in the lab.
B) Astronomers have sent spacecraft through the event horizon of a nearby black hole.
C) Astronomers have analyzed the light from matter within the event horizon of many black holes.
D) Astronomers have detected X-rays from accretion disks around black holes.
E) We don't know for sure: we only know what to expect based on the predictions of general relativity.