一次性造成5万元以下经济损失的，属（）事故。
A.一级事故
B.二级事故
C.三级事故
D.四级事故
参考答案：D
句型转换。
1. I like this new watch. (改写为一般疑问句)
___________ ___________ like this new watch?
2. He has a basketball. (改写为否定句)
He ___________ ___________ a basketball.
3. She has a new volleyball. (改写为一般疑问句)
___________ she ___________ a new volleyball?
4. He has some interesting collections. (就画线部分提问)
___________ ___________ he ___________?
5. Do you play basketball? (作否定回答)
___________, I ___________.
对如下二叉树
进行后序遍历的结果为______。
A．ABCDEF
B．DBEAFC
C．ABDECF
D．DEBFCA
进行后序遍历的结果为______。