Answer :
In the role where Jimmy Carter established the Carter Center, helped oversee democratic elections in other nations, worked to eradicate contaminated water-based diseases, and collaborated with Habitat for Humanity to provide homes for those in need is "Past-President."
1. Jimmy Carter established the Carter Center after his presidency to promote peace, advance human rights, and improve global health.
2. He has been involved in monitoring democratic elections in various countries to ensure fairness and transparency in the electoral process.
3. Carter has worked tirelessly to eradicate diseases caused by contaminated water, such as Guinea worm disease, through public health initiatives.
4. Through his involvement with Habitat for Humanity, Carter has contributed to building homes for people in need, emphasizing the importance of affordable housing and community development efforts.
Therefore, based on these activities and initiatives, the most appropriate role for Jimmy Carter in this context is "Past-President."