热影响区最高硬度试验法主要用在相同试验条件下不同母材冷裂倾向的相对比较。( )
参考答案：对
有功功率与视在功率的比值称为( )。
A．功率因数
B．品质因数
C．传输效率
D．负载系数
The number of the students in our grade ________about six _______,
of them are girls.
A．are, hundreds, two- thirds
B．is, hundred, two- third
C．is, hundred, two thirds.
D．are, hundreds, two third
