Open Market Operation is a tool of monetary policy in which the Federal Reserve buys and sells government securities. It is the major tool the Fed uses to affect the supply of reserves in the banking system. The market is open, which means that the Fed doesn’t decide on its own which securities dealers it will do business with.
The action that has come to symbolize the end of the Cold War is 3. tearing down the Berlin Wall. The Wall had been formed by the Soviet Union to separate East Berlin (Soviet-controlled) from West Berlin (Western-controlled). Its fall allowed Berliners (and Germans) from the Eastern half finally make their way to the Western half.
If you are talking about the first air pollution problem its is A, almost about 100 years ago.
1955
