Bob is ______eleven—year—old boy，but he knows a lot about Chinese history．

A．an                       B．a                         C．the                 D．／

（2006，盐城）Bob is ________ eleven-year-old boy, but he knows a lot about Chinese history.

1. A.
   an
2. B.
   a
3. C.
   the
4. D.
   /