Travelers onboard a spaceship are moving at 0.9c from one star to another. The stars are at rest relative to each other, and this is the speed of the spaceship relative to the stars. Which of the following statements are true? Assume observers on the spaceship or on the stars are in inertial reference frames. 

(a) Observers at rest with respect to the stars measure a shorter distance between the stars than the travelers do. 

(b) The observers see the travelers moving in slow motion relative to themselves. 

(c) The observers see the travelers age more slowly than they themselves do. 

(d) The travelers measure a shorter distance between the stars than the observers do. 

(e) The travelers believe they are aging more slowly than the observers are.