两个互相啮合很好的渐开线齿轮，如忽略各制造和安装上的误差，其分度圆应（）。
A、相交
B、相切
C、夹角
D、重合
参考答案：B
After the new technique was introduced，the factory produced ________ tractors in 1988 as the year before.
A．as twice many
B．as many twice
C．twice as many
D．twice many as
产品质量由几方面的质量特性反映的结果？
