Explanation:

- The passage discusses the importance of maintaining various aspects of health and urges action to ensure wellness.

- Option 1: "may" implies a possibility or permission, which doesn't convey the urgency or necessity needed in the context.

- Option 2: "must" indicates an obligation, a strong necessity, or duty, perfectly fitting the imperative tone of the passage.

- Option 3: "could" suggests a potential or a possibility, which is too weak for the context that stresses on necessary actions.

- Option 4: "can" suggests ability but lacks indication of necessity or obligation that the passage implies.