车刀前角越大,主切削力越小。主偏角加大时,主切削力减小,当主偏角为()°时,主切削力最小。
A.50~60°
B.60~70°
C.60~75°
D.70~80°
参考答案:C
Can you play the violin? ______. But I can sing.
A.Yes,I do
B.No,I don’t
C.Yes,I can
D.No,I can’t
输卵管妊娠最常见的原因是()
A.内分泌失调
B.受精卵游走
C.输卵管慢性炎症
D.输卵管手术粘连
E.精神神经功能紊乱