问题

One _______ fact is _______ Crystal always keeps a toothbrush in his pocket for good luck when he is the host of the Academy Awards.
A:little-knowing ; 不填
B:well-known ; which
C:little-known ; what
D:little-known ; that
B:well-known ; which
C:little-known ; what
D:little-known ; that
正确答案是: