The north american air mass is a large body with generally uniform temperature and humidity. the area from which air mass originates is called source region. the air mass source regions range from extensive snow covered polar areas to deserts to a tropical oceans.
Answer:
Wars, battles, draughts, and viruses.
Explanation:
In history many people faced tough wars and battles like the revolutionary war, world war, etc.
Draught has caused many people to die in history because of the lack of water they had, this most commonly occurred in desert areas.
Viruses like the Plague spread like a wildfire and were as deadly as a snake bite. This virus is the cause for many deaths in history.
After the World War II, America as a nation stopped
producing gunnery and bombs and resorted in creating peaceful industrial
employments. The American economy have grown that labor force grew from 60
million to 111 million on year 1948 to 1982 and grew from 58 million to 99
million.
