Final answer:
Volunteering your time to a charity and posting your experiences to motivate others is the best demonstration of social media being used as a health tool.
Step-by-step explanation:
The best demonstration of social media being used as a health tool would be option d) Volunteering your time to a charity and posting your experiences to motivate others.
Volunteering your time to a charity and sharing your experiences on social media can inspire others to get involved and make a positive impact on their health and well-being. By showcasing the benefits of volunteering and the personal fulfillment it brings, you can encourage others to prioritize their own health and find ways to contribute to their community.