单项选择题
A.b/hg≥φB.b/hg>φC.b/hg≤φD.b/hg=φ
A.磨合期B.磨合延长期C.正常工作时期D.极限磨损时期
A.B/2hg≤φB.B/2hg>φC.B/hg>φD.b/2hg=φ