If you stay on earth while a friend races off in a rocket at a speed close to the speed of light, then according to special relativity you will see a clock on the rocket appear to click more slowly than the one on your wall. If your friend looks back at your clock , then according to the same theory the friend will see your clock appear to tick.

A-At the same speed of the clock on the rocket

B-faster then the clock on the rocket

C-Faster or slower than the clock on the rocket, depending on the direction of travel of the rocket compared with earth

D-slower than the clock on the rocket.