The correct answer is:
The decision by Congress in 1873 to stop buying and minting silver.
The Coinage Act of 1873, signed into law by President Ulysses S. Grant, was a general reform of the laws associated with the Mint of the United States.
The act was later criticized by advocates of bimetallism as the "Crime of '73" because it ended bimetallism in the United States, by setting the nation on the gold standard.
The Scramble for Africa refers to the period between roughly 1884 and 1914, when the European colonisers partitioned the – up to that point – largely unexplored African continent into protectorates, colonies and ‘free-trade areas’. At the time the colonisers had limited knowledge of local conditions and their primary consideration was to avoid conflict among themselves for African soil. Since no one could foresee the short-lived colonial era, the border design – which endured the wave of independence in the 1960s – had sizable long-lasting economic and political consequences. The Scramble for Africa resulted in several large countries characterised by highly heterogeneous geography and ethnically fragmented populations that limit the ability of governments to broadcast power and build state capacity.
The answer it’s number 4 “implied power”
