高速钢刀具用于承受冲击力较大的场合，常用于高速切削
参考答案：错
---_____ do you read English newspapers? ---I read China Daily every day.
A．How long
B．How soon
C．How often
D．How far
无向图的邻接矩阵是
A．对角矩阵
B．稀疏矩阵
C．上三角矩阵
D．对称矩阵
