单项选择题

A.250mg/L有效氯消毒剂浸泡30min
B.250mg/L有效氯消毒剂浸泡60min
C.500mg/L有效氯消毒剂浸泡30min
D.500mg/L有效氯消毒剂浸泡60min
E.1000mg/L有效氯消毒剂浸泡30min