机械零件产生疲劳现象的原因是材料（）有缺陷。
A、表面
B、表面和内部
C、内部
参考答案：B
They asked the government to make ______clear to the public ______ they did was right.
A．it; that what
B．it; that
C．that; what
D．this; that
简述Partnering模式的特征、要素和适用情况。
