What organ do we use to store air/breathe?

Consider the last statement in the prompt: "people take such environmental factors into account in their choices when deciding where to live." do all people have a choice as to where they live? what factor plays a key role in this decision and may therefore play a large role in determining quality of life?

What causes darkening of the skin as melanin production increases

This part insulates the reaction chamber from the transfer of heat to or from the surrounding environment