Because door of world is open for all..
and so U.S entered WW1
Answer:
the think the answer is A
Explanation:
Answer:
Europe's Medieval Agricultural Revolution
Explanation: Crop yields multiplied by at least threefold. Europe's population followed suit, tripling in less than three centuries. The average European lifespan increased by as much as two decades. Towns and cities reemerged, and with them came new crafts and a revival of trade.