长江沿江地带城市的形成和发展与 关系密切，这里有全国最大的城市 。
河流 上海
Don't make so much noise. The children _____ an English lesson. [ ]
A. have
B. are having
C. were having
对一棵排序二叉树进行( )时，可以得到有序序列。
A．前序遍历 B．中序遍历C．后序遍历 D．层次遍历
