Which of the following is a characteristic of M1?

M1 is a key measure of the money supply in an economy, primarily representing the most liquid forms of money. It includes physical currency (such as coins and paper money) that is in circulation and checking accounts that allow for immediate access to funds. Since checking accounts can be readily used for transactions, they are considered part of the most liquid assets.

The composition of M1 focuses specifically on assets that can be quickly converted to cash or used directly for payments. Including elements like savings accounts or time deposits, which are part of M2 but not M1, would misrepresent the characteristics of M1, as those funds typically require more time to access.

Therefore, the characteristic that M1 includes checking accounts and currency aligns accurately with its definition as a measure of liquid money in the economy. This makes option A the correct choice.