工艺系统刚度定义为被加工表面法线上作用的切削分力与该方向刀具、工件的相对（）的比值。
A、距离和密度
B、密度
C、位移
D、体积
参考答案：C
一质量为2kg的固体物体，将其运到月球上后，其质量为 _________ kg，如果它熔化后变成了液态，其质量会_________；给此物体加热，其密度会_________（选填“增大”、“减小”、或“不变”）．
(1) ________What are the boys fighting about with each other?
(2)______People often have to fight for their liberty.
(3)________He fought against cancer and lived to be eighty.
(4)_______She fought back her tears and went on writing.
(5)________He fought with his classmate yesterday.
(6)________England fought with France against Germany in the First World War.
