If a supply shutoff valve was closed for less than five minutes ho maintenance is required and shutoff periods are hot accumulative.如果供应关闭阀关闭时间少于5分钟，则需要进行维护，关闭时间为热累积。
A.If a supply shutoff Valve was closed within five minutes of maintenance performance is needed and shutoff periods are hot accumulated. B.Maintenance action is not necessary and shutoff periods are not calculated unless the shutoff valve was closed for less than five minutes C.When a supply shutoff valve was closed for five minutes, maintenance action is hardly required, and shutoff duration are not included.正确答案A
