机械除锈法多适用于铸件和厚板材的处理。
参考答案：对
Although the causes of cancer ________, we do not yet have any practical way to prevent it．
A．have uncovered
B．have been uncovering
C．are uncovering
D．are being uncovered
把下列数改写成用“万”或“亿”作单位的近似数
776500≈
8354900≈
2948009546≈
9995643≈
96987003000≈
59258006900≈
