Choose the correct tense for the sentence: 'If he _____ earlier, he would have avoided the traffic jam.'

在二叉树中，如果一个节点的左子树和右子树都为空，则该节点被称为？

In the context of regulatory changes, which of the following statements best reflects the potential challenges faced by a regulatory body when under pressure from external stakeholders?

Identify the correct subjunctive mood structure: The professor suggested that the student ______ more attention to symbolic meanings.

在遍历线索二叉树时，若当前结点p的右线索标记为1，以下哪项操作是正确的？