Final answer:
Marketable securities represent ownership or debt of firms and government debt, while demand deposits are checkable deposits that are available for withdrawal or check writing.
Step-by-step explanation:
Marketable securities represent either ownership or debt of publicly held firms and government issued debt, in the form of bonds, notes, and bills. Demand deposits, on the other hand, are checkable deposits in banks that are available by making a cash withdrawal or writing a check. They are considered part of the M1 money supply, which also includes currency in circulation. These demand deposits are called demand deposits or checkable deposits because the banking institution must give the deposit holder his money 'on demand' when the customer writes a check or uses a debit card.