The Highest-Energy Cosmic Rays That Reach Earth

Multiple Choice

The highest-energy cosmic rays that reach Earth

A) could actually originate outside the Milky Way Galaxy.
B) are produced in particle accelerators here on Earth.
C) emerge from the supermassive black hole at the center of the Milky Way.
D) are in fact X-ray and gamma-ray photons.
E) are the best candidates for explaining dark matter.