义务教育具有强制性的特点，所以又叫强迫教育。
参考答案：对
I never answer his calls and I ignore him every time I see him, hoping that he'd get the _____.[ ]
A. information
B. news
C. message
D. word
某二叉树中度为 2 的结点有 18 个，则该二叉树中有_________个叶子结点。
