The narrowest definition of the money supply (M1) includes:

a. cash and travelers' checks.

b. cash, travelers' checks, and savings account balances.

c. cash, checking account balances, and travelers' checks.

d. cash, bank deposits, and money market accounts.

c. cash, checking account balances, and travelers' checks.

Explanation:

Money Supply is the concept that means the amount of the liquid financial products and total currency in the market or economy. It is regulated the macro-economically by the monetary policy. So, there are types of measures of money supply or stock:

-M0: narrowly, it means the hard currency in circulation

-MB: it equals M0 + the hard currency which are not technically in circulation and in bank reserves.

-M1: it is the most common one and equals M0 plus checking accounts plus travelers' checks and other checkable deposits.

-M2: covers M1 and saving accounts and CDs.

-M3: it surrounds the larger deposits.

-MZM: finally, this indicates the money market deposits.

That's why we could notice that M1 narrowly means the cash, checking account and travelers' checks.