How does visualization promote relaxation and stress reduction?

a.) it enables you to make the world "go away" for a while
b.) it reminds you of other tasks you need to complete
c.) it encourages your friends and family to stay away
d.) it produces chemicals in your muscles

C.when you are visualizing, you are no longer focused in reality.

Because During the visualisation, you would create a special place in your head that represent the ideal situation which you want to achieve. During stressful situation, this would help you go away from the stress and make your mind enter a state of calmness and relaxation.