单项选择题
A.≥Im B.≥1.2m C.≥1.5m D.≥2m
A.10-30mm B.10-20mm C.20-30mm D.20-35mm
A.∮≤300mm B.∮≤200mm C.∮≤250mm D.∮≤280mm
A.∮>350mm B.∮>300mm C.∮>380mm D.∮>320mm
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