单项选择题 Upon the completion of required tests, a （） should be placed on each extinguisher, showing the date and the person who completed the tests.

单项选择题 If you must enter a room or compartment to combat the fire, keep an escape path （）.

单项选择题 According to the international regulations concerning the prevention of pollution of sea areas from ships, the disposal into the sea of all plastics is （）.