单项选择题
A.孔深<1.8 B.1.8≤孔深<2.5 C.2.5≤孔深<5.0 D.孔深≥5.0
A.4~6 B.6~7 C.7~8 D.8~9
A.70~80 B.75~85 C.80~90 D.80~95
A.1/2 B.1/3 C.1/4 D.1/5
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