1.What is the depth of the tree in the Figure ？
Answer:树的深度=根节点到最远叶子的距离，最远：A-B-E-J-L(M),有四条边，所以树的深度为4.
2.Give the prefix, infix, and postfix expressions corresponding to the tree in the figure.
Answer:先序遍历：先节点–再左子树–再右子树；
中序遍历：先左子树–再节点–再右子树；
后序遍历：先左子树–再右子树–再节点.
prefix:-**ab+cde;
infix:((ab)(c+d))-e;
postfix:ab*cd+*e-
3.a. Show the result of inserting 3, 1, 4, 6, 9, 2, 5, 7 into an initially empty binary search tree.
b. Show the result of deleting the root.
Answer:a.二叉查找树以中序遍历的方式遍历，按照中序排列规则插入元素画出图像即可；
b.根节点有两个直接相连的子节点，用右边子树上的最小元素替换该节点即可.