Which of the following explains the debit and credit rules relating to the recording of revenue and expenses?

a. Expenses appear on the left side of the balance sheet and are recorded by debits; revenue appears on the right side of the balance sheet and is recorded by credits.

b. Expenses appear on the left side of the income state- ment and are recorded by debits; revenue appears on the right side of the income statement and is recorded by credits.

c. The effects of revenue and expenses on owners' equity.

d. The realization principle and the matching principle.