单项选择题
A.≥10 B.≥15 C.≥20 D.≥30
A.≤0.1s B.≤0.2s C.≤0.25s D.≤0.3s
A.5mm，40mm B.5mm，30mm C.10mm，40mm D.10mm，30mm
A.65 B.66 C.67 D.68
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