The correct answer is: D. mortgages
A mortgage is a loan that is secured by the borrower’s property. The lender, usually a bank, agrees to lend the borrower money to buy a property, and the borrower agrees to repay the loan over time, with interest. If the borrower fails to repay the loan, the lender can foreclose on the property and sell it to repay the debt.
Municipal bonds are bonds issued by state and local governments. They are considered to be relatively safe investments, and they are often exempt from federal income tax.
Corporate bonds are bonds issued by corporations. They are considered to be riskier investments than municipal bonds, but they also offer the potential for higher returns.
U.S. Treasury bonds are bonds issued by the U.S. government. They are considered to be the safest investments available, and they are backed by the full faith and credit of the U.S. government.