单项选择题
A.15%~20%B.15%~25%C.20%~25%D.25%~30%
A.30minB.15minC.60minD.5min
A.DN≤80mmB.DN≤100mmC.DN>25mmD.DN≤50mm
A.DN≤30mmB.DN>20mmC.DN≤25mmD.DN>50mm
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