A European option is different from an American option in that

A、American options have a fixed exercise price; European options' exercise price is set at the average price of the underlying asset during the life of the option.
B、European options tend to be worth more than American options, ceteris paribus.
C、European options can only be exercised at maturity; American options can be exercised prior to maturity.
D、one is traded in Europe and one in traded in the United States.