Which of the Following Statements About Revenue and Expense Accounts

Which of the following statements about revenue and expense accounts is correct?

A) Revenue accounts are a subset of assets,and expense accounts are subcategories of liabilities.
B) Both revenue accounts and expense accounts are subcategories of assets.
C) Both revenue accounts and expense accounts are subcategories of Retained Earnings.
D) Revenue accounts are a subcategory of Cash and expense accounts are a subcategory of Accounts Payable.