Which condition represents the appropriate time for setting off distress flares and rockets? （）

A.Only when there is a chance of their being seen by rescue vessels

B.At half hour intervals

C.At one hour intervals

D.Immediately upon abandoning the vessel

十、五、三车距离信号其速度要求分别为（）。（B、3、X）[05-00-03-01][020103]

A.10km/h、7km/h、5km/h

B.15km/h、10km/h、5km/h

C.15km/h、10km/h、3km/h

D.10km/h、5km/h、3km/h