一般切削速度越低或进料速庋越快，木材加工的光洁度越高，反之，越差。
参考答案：错
—John sings so well. Has he ever been framed?
—No. He learns all by himself. He _____ goes to any training class. [ ]
A. usually
B. often
C. never
D. even
尾纤活动连接器的连接不好，很容易产生（），造成连接损耗较大。
A．后向散射曲线增大
B．曲线误差大
C．长度不准确
D．光纤端面分离
