The United States personal income tax system is
\textcircled{a}. progressive, which means that it moves forward in pace with ever-changing societal norms
\textcircled{b}. progressive, which means that higher income levels have higher tax rates
\textcircled{c}. a competitive system, meaning that it is updated annually to keep pace with countries around the world
\textcircled{d}. a market structure, meaning it is designed to help keep the economy stabilized.
\textcircled{e}. a regressive system, which means that the highest earners pay the lowest amount of tax