Answer:
The last man on Earth received a phone call, who was the caller?
I am the minerals vital for your good health.
I jump when I walk and sit when I stand. What am I?
What has one eye but cannot see?
I am a path between high natural masses; remove the first letter to get a path between man-made masses.
Whoever made me don't want me. Whoever bought me don't need me. Whoever use me don't know me.