Suppose One Twin Takes a Ride in a Spaceship Traveling

Suppose one twin takes a ride in a spaceship traveling at a very high speed to a distant star and then back again, while the other twin remains on Earth. Compared to the twin who remained on Earth, the astronaut twin is

A) older than the Earth-twin.
B) younger than the Earth-twin.
C) the same age as the Earth-twin.
D) The ages cannot be determined from the information provided.