He basically meant the Iron Curtain as a not physical boundary after WW2, where many communist nations all functionally enforced a barrier between the rest of the world and them. The best representation of this is the Berlin Wall, where one side was democratic and the other communist, and it was nearly impossible to get to the other side without having serious consequences.
Church hill stated in a speech "A shadow has fallen across the scenes so lately lighted by Allied victory. From Stettin in the Baltic to Trieste in the Adriatic, an iron curtain has descended across the continent." We know that there was a a conference called the Potsdam Conference where the Allie powers of Great Britain, France, the U.S., and the Soviet Union agreed that Germany was going to be divided into four occupation zones, and each country would get one. There was a political divide between West Europe and Communist Europe. Western Germany was now a capitalist country and Eastern Germany was now a communist country. So what Church hill meant when he metaphorically said "iron curtain" he meant a political divide between Western and Eastern Europe.
I believe the answer would be A. Levees held back and annual floods of the Tigris and Euphrates Rivers. And B. Surplus barley and wheat could be traded for other things.
The land of Maryland was the only thing standing between Virginia and the Union capital at Washington D.C. The war would have gone very differently had Maryland seceded from the Union. Maryland voted to abolish slavery during the war in 1864.
