Final answer:
Measures of income influencing demand include an individual's specific period earnings, wealth level, and after-tax income, making all provided options correct.
Step-by-step explanation:
When considering influences on demand, measures of income include an individual's earnings in a specific time period, an individual's level of wealth, and an individual's after-tax income. Therefore, E. Answers a, b, and c are all correct is the accurate option. Income influences the quantity of goods and services demanded in the market. Goods for which demand increases when income increases are referred to as normal goods, whereas goods for which demand decreases as income increases are called inferior goods.