Final answer:
Nuclear power has the highest start-up costs compared to coal, natural gas, and oil due to its complex infrastructure and long-term waste management needs.
Step-by-step explanation:
The nonrenewable energy source that would have the highest start-up costs to become operational is nuclear power. This is because the costs associated with nuclear power are dominated by up-front costs, such as the construction of the power plant, as well as the technology needed to ensure safety and to manage the radioactive waste responsibly over long periods. In contrast, fossil fuels like coal, natural gas, and oil generally have lower initial costs, as they primarily rely on extraction and refining processes rather than complex and expensive infrastructure and long-term waste management.