In the aftermath of the downturn in the early​ 1930s, private banks​ ____________; between 1936 and 1937 the Fed raised the​ _________, which​ ___________ the Great Depression.
A. Increased their holdings of excess​ reserves; reserve​ requirements; prolonged
B. Increased their holdings of risky​ securities; risk assessment​ parameters; shortened
C. Reduced their holdings of excess​ reserves; discount​ rate; shortened
D. Reduced their excess​ reserves; reserve​ requirements; prolonged