The Bretton Woods system ended when: A. several countries tied the value of their currencies to the U. S. dollar. B. the United States decided to stop backing the U. S. dollar with gold reserves C. the United States experienced its second Industrial Revolution
D. the gold standard became more popular in countries around the world​

B

Explanation:

There is no other answer but B. That was Nixon's doing. He took the American dollar off the Gold system. Gold in 1980 eventually went from 35 dollars to 800 which is a stupendous move. Many people, unfortunately for them, bought at the top and it took 31 years (I think) for them to recover their money.

the first successful, urban blues recording, selling more than 75,000 copies, was made in year 1920.

mamie smith recorded the first commercially successful example of the urban blues,   with the recording of “crazy blues”."crazy blues" was recorded on august 10, 1920, in new york city. within a month of the release of “crazy blues” it had sold 75,000 copies.

you have to put the parentheses like this:

in fact, you have to perform the operation inside parentheses first, and then proceed in order: