Explanation:

- An expenditure on health refers to the cost incurred in maintaining or improving health through buying medical services or products.

- An investment in health implies putting resources into health-related activities or interventions that are expected to yield future benefits, such as improved work performance and productivity.

- Both a and b: This option considers health spending as both an expense and an investment, recognizing that money spent on health can be immediately beneficial and provide long-term productivity gains.

Correct Answer: Option 3 - Both a and b