单项选择题
A.100kPa B.200kPa C.300kPa D.400kPa
A.10kPa B.15kPa C.20kPa D.25kPa
A.15～20mm B.15～30mm C.15～40mm D.15～50mm
A.30% B.40% C.50% D.60%
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