Final answer:
Ronald Reagan's threefold agenda upon taking office in 1981 included tax cuts, deregulation of the economy, and reduction in spending for social programs, but not a reduction in the power and activism of the presidency. His economic policies, known as Reaganomics, aimed to stimulate investment and growth, though they ultimately failed to balance the federal budget.
Step-by-step explanation:
Ronald Reagan came into office in 1981 with a threefold agenda, which included tax cuts, deregulation of the economy, and reduction in spending for social programs. However, one aspect that was not part of his initial agenda was reducing the power and activism of the presidency. In fact, Reagan used his presidential power to advance his goals, such as increasing defense spending significantly. The answer to the question, which asks which agenda was not part of his initial plan upon taking office is C. reduction in the power and activism of the presidency.
Reagan's policies, popularly known as Reaganomics, were largely based on the supply-side economics theory. He implemented significant tax cuts, particularly for the wealthy, with the idea that this would spur investment and economic growth. While Reagan did succeed in cutting taxes and pursuing deregulation, he failed to balance the federal budget and actually increased the size of the federal government in several areas, including defense.