Final answer:
The relationship between income and political participation in the United States is that higher income correlates with higher political participation.
Step-by-step explanation:
The correct statement that describes the relationship between income and political participation in the United States is a) Higher income correlates with higher political participation.
Research has shown that individuals with higher incomes are more likely to vote compared to those with lower incomes. People earning below the median income are less likely to vote than those earning above the median income. This can be attributed to factors such as the belief that their vote does not influence political outcomes and barriers to voting faced by low-income individuals.