Everyone sitting in the waiting room of the school' s athletic office this morning at nine o' clock had just registered for a beginners tennis clinic. John, Mary, and Teresa were all sitting in the waiting room this morning at nine o' clock. No accomplished tennis player would register for a beginners tennis clinic. It the statements above are true, which one of the following must also be true on the basis of them?
A: John, Mary, and Teresa were the only people who registered for a beginners tennis clinic this morning.
B: John, Mary, and Teresa were the only people sitting in the waiting room of the school's athletic office this morning at nine o'clock.
C: Neither John nor Teresa is an accomplished tennis player.
D: None of the people sitting in the school's athletic office this morning at nine o'clock had ever played tennis.
Choose A, B, C or D as your solution.
C