单项选择题
A.4.5±0.7B.5±0.7C.5.5±0.7D.6±0.7
A.自上而下B.自下而上C.先竖缝后横缝D.先横缝后竖缝
A.2minB.5minC.10minD.15min
A.1B.2C.5D.10
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