单项选择题
A.30 B.35 C.50 D.28
A.100N,20mm B.150N,30mm C.100N,30mm D.200N,30mm
A.1.4,0.6 B.1.8,0.35 C.1.5,.0.6 D.1.4,0.5
A.1 B.2 C.3 D.4
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