m阶B树的根结点若不是叶结点，那么它至多有m棵子树，至少有2棵子树。那么它的中间结点至少有______棵子树。
参考答案：m/2
为明确诊断应做下列哪项检查
A．胸部X线摄片B．痰细菌学检查C．肺功能测定D．血常规检查E．血肝肾功能检查
---I’d like to buy a book named Confucius from the Heart.
-- Sorry, it ________ two days ago.
A．is sold out
B．has been sold out
C．was sold out
D．sold out
