Final answer:
The Great Depression and World War II were periods that saw an enormous expansion of presidential authority, largely due to President Franklin D. Roosevelt's New Deal programs and wartime measures.
Step-by-step explanation:
During the major event of The Great Depression, there was an enormous expansion of presidential authority. President Franklin D. Roosevelt (FDR) came into office during this time and implemented the New Deal, a series of programs and policies designed to bring economic relief, recovery, and reforms to the United States. This period saw a significant growth in the federal bureaucracy and the scope of government involvement in the economy and social welfare, which expanded the role of the federal government in the lives of American citizens, effectively increasing presidential power. Additionally, World War II further expanded presidential authority with various wartime agencies and boards created to manage the war effort and the economy. Therefore, the answer is A) The Great Depression and C) World War II.