Why do marathon runners "carbo load" (that is, eat a lot of pasta) before a big race?

A)They will feel full longer.
B)The bonds in carbohydrates have high potential energy.
C)The bonds in carbohydrates have low potential energy and can thus be broken down and readily consumed.
D)Through the process of anabolism, the athlete will break down the carbohydrates into smaller components, including ATP.