— What's the matter?  

— She caught         bad cold and had to stay in         bed.[ ]

A. the; the

B. a; the

C. a; a

D. a; 不填

有下列二叉树，对此二叉树中序遍历的结果为( )。

A．ABCDEF

B．BDAECF

C．ABDCEF

D．ABCDFE