Final answer:
The highest spending priority for the federal government in 2010 was national defense.
Step-by-step explanation:
Based on the provided information, the highest spending priority for the federal government in 2010 was national defense. National defense, along with Social Security, healthcare, and interest payments, accounted for roughly 73% of all federal spending during that time period.
The remaining 27% was allocated to other categories such as international affairs, science and technology, natural resources and the environment, transportation, housing, education, income support for the poor, community and regional development, law enforcement and the judicial system, and administrative costs of running the government.