含矸率是指粒度大于()的矸石量占全部煤量的百分数。
A.50mm
B.25mm
C.13mm
D.6mm
参考答案:A
I am really worried about his grades in the coming test because of the little use he _____ of his spare time
before it. [ ]
A. did
B. took
C. got
D. made
感应加热表面淬火时,如何防止轴类零件或长条形零件的变形?