I believe the answer is: c. It enables you to make the world "go away" for awhile.
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.
when the grade that you already have were to be put on your report card it would be rounded to the nearest whole number, that being a 70%. so really any grade would help.
