Answer:
b. upper middle class
Step-by-step explanation:
We know working class, is the regular, average class and is not the rare individuals that are considered rich or high income. We also know it can't be working poor, as poor is pretty much the complete opposite of high-income or in other words rich. Upper middle class seems to be the most valid option as upper means higher up, more richer, and higher-income then the average class.