The sailors should show relevant flags by day or pilot lamps at night.

The sailors should show relevant flags by day or pilot lamps at night.
The sailors should show relevant flags by day or pilot lamps at night.

The sailors should show relevant flags by day or pilot lamps at night.
水手应该在白天挥动相关的旗帜或者在晚上打出指示灯

船员应该在白天展示有关的旗帜，到了晚上舵手要亮灯。