Which of the following is an example of what can serve as collateral?

Collateral refers to an asset that a borrower offers to a lender to secure a loan or credit. In the event that the borrower defaults, the lender can seize the collateral to recover their losses. Among the options provided, savings accounts are a tangible form of collateral. They represent actual funds that can be frozen or accessed by the lender if the borrower fails to meet their obligation.

The other choices do not hold the same value as collateral. Friendship and verbal agreements are intangible and lack legal enforceability in a financial setting. A signature, while important in agreeing to terms, does not constitute physical assets that could be claimed by a lender. Thus, a savings account clearly provides a secure measure of protection for the lender, making it the correct choice for what can serve as collateral.