The answers are Gross domestic product
Quality of life
And literature
For humans, population density is the number of people per unit of area, usually quoted per square kilometer or square mile (which may include or exclude, for example, areas of water or glaciers). Commonly this may be calculated for a county, city, country, another territory or the entire world.
Answer:
are telescopes that can take images of invisible energy
observe electromagnetic radiation that is blocked by our atmosphere
Explanation: