Please choose the correct ending to complete the given sentence: Sports and Fitness: [header] How to stay underwater longer [title] Start a cardiovascular exercise routine. [step] The best way to increase the amount of time you can stay underwater is by increasing your cardiovascular ability. By committing to a cardio training exercise routine, you'll increase your body's ability to process and use oxygen.

Ending1: [substeps] Do cardio 1 hour a day, even if you're not very active. Studies have shown that people who engage in cardio exercise their entire lives have lower cholesterol levels, which can help them go longer. Ending2: [substeps] Commit to running, powerwalking, using an elliptical, or another cardio activity. Exercise 3 to 5 times a week for at least 30 minutes. Ending3: This will help you to stay underwater longer, and even help prevent injury. You want to make sure that you've kept up your cardio pace as much as possible, without injury. Ending4: Take the following steps to start a cardiovascular workout regimen : [substeps] Start with a short run at a medium pace for 30 seconds. Running for 30 seconds is about the same as hopping 3 times--you increase speed in that time period.

Answer format: ending1/ending2/ending3/ending4