Which of the Following Describes a Major Danger of Interstellar

Multiple Choice

Which of the following describes a major danger of interstellar travel at near light speed?

A) Any interstellar journey will take much longer than the lives of the crew members.
B) Time dilation will slow the heartbeats of the crew to a dangerously low rate.
C) Atoms and ions in interstellar space will hit a fast-moving spacecraft like a flood of dangerous cosmic rays.
D) Asteroid fields floating in interstellar space will present a navigational challenge.
E) Supernova explosions will destroy spaceships passing nearby.