The correct answer is:
D. Migration can alter the age distribution by increasing the number of working-age individuals, potentially affecting economic growth and dependency ratios.
Migration can significantly reshape the demographic structure of a country over time by influencing factors such as age distribution, gender composition, and the balance between urban and rural populations. An influx of working-age individuals can enhance the labor force, stimulate economic growth, and affect dependency ratios by lowering the percentage of dependents relative to the working population.