Please choose the correct ending to complete the given sentence: Health: [header] How to not fall down stairs [title] Pay attention. [step] Going down stairs is done so frequently that many accidents are caused by not paying attention to the stairway environment. Research suggests that people tend to look only at the first three steps of a stairway, rather than at each step.

Ending1: When walking down unfamiliar stairs, be careful to attend to each step. [substeps] In older stairways, stair depth may vary. Ending2: Byn't paying attention, you may be preventing yourself from setting the proper example. You are more likely to fall downstairs if you pay attention and notice when you slip and drop a step. Ending3: By paying attention to the stairs, you are aware what is going on next. [substeps] Pushing into a fell staircase can cause serious injury to your body, which usually leads to you having to take a serious jump to correct your fall. Ending4: When they're not paying attention, the stair treads " go down " towards where they are supposed to be. If you're going down with someone, wait at least 5 minutes after saying that you're heading down the stairs before proceeding.

Answer format: ending1/ending2/ending3/ending4