ALeft first and then right先左后右
BRight first and then left先右后左
CIn stack simultaneously同时入栈
DOnly the left subtree is stacked, and the right subtree is not stacked只有左子入栈，右子不入栈
问题：
[单选题]If in the pre-order traversal the access to the root node is followed by accessing the right subtree first and then the left subtree, then the stacking order of the left and right subtrees is:若在先序遍历中规定访问完根节点后先访问右子树再访问左子树,则左、右子树的入栈顺序是：
ALeft first and then right先左后右
BRight first and then left先右后左
CIn stack simultaneously同时入栈
DOnly the left subtree is stacked, and the right subtree is not stacked只有左子入栈，右子不入栈
ALeft first and then right先左后右
BRight first and then left先右后左
CIn stack simultaneously同时入栈
DOnly the left subtree is stacked, and the right subtree is not stacked只有左子入栈，右子不入栈
答案解析：