Please choose the correct ending to complete the given sentence: Health: [header] How to fill an oxygen tank [title] Replace the oxygen if the pressure gauge is in the red. [step] The pressure gauge is the large gauge at the top of the oxygen tank. This gauge has a dial that indicates how full the oxygen tank is.

Ending1: If the dial points to the red area or just above the red area, it is time to refill your oxygen tank. [title] Turn on both your oxygen concentrator and your fill system. Ending2: The dial reads 9 feet (1.8 meters) per minute. [substeps] In contrast, you can find your oxygen level at the bottom of the oxygen tank. Ending3: The dial you use should be indicated on the tank's roof. [substeps] If the dial reads " 100, " that means you are filling the tank too full. Ending4: The dial will be labeled " 80-4 ". If your pressure gauge is in the yellow zone, you can use the lcm gauge here instead.

Answer format: ending1/ending2/ending3/ending4