M7/h6配合代号的含义是（）。
A.基孔制间隙配合
B.基轴制间隙配合
C.基孔制过渡配合
D.基轴制过渡配合
参考答案：D
He was busy writing a story, only ______ once in a while to smoke a cigarette. [ ]
A. to stop
B. stopping
C. to have stopped
D. having stopped
建筑工人有时需人力拖动预制板，他们常常会在预制板下塞两只圆木棍，为什么要这样做？
