Final answer:
To represent a withdrawal of $20 from a bank account, the value that can be used is -$20.
Step-by-step explanation:
To represent a withdrawal of $20 from a bank account, the value that can be used is C. -$20.
A negative value is used to represent a withdrawal because it indicates a decrease in the account balance. The negative sign indicates that money is being taken out of the account.
For example, if you have a bank account balance of $100 and you withdraw $20, your new account balance would be -$20, indicating that you owe the bank $20.