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