Which of the following is not a correct statement about financial statements?

a. Revenue refers to increases in a firms assets resulting from the sale of stocks, or other activities intended to earn income.

b. Expenses are resources used up as the result of business operations.

c. Accrual-basis accounting recognizes revenue when it is earned and matches expenses to the revenues they helped produce.

d. Main sources of a firms income are sales revenue and investment income.

e. Main sources of expenses are cost of goods sold (CGS) and operating expenses.