The correct answer is: D. treasury bonds
Treasury bonds are considered to be the safest type of investment because they are backed by the full faith and credit of the United States government. This means that the government is legally obligated to repay the bondholders, even if it means raising taxes or cutting spending.
U.S. bonds are also considered to be a safe investment because the United States has a long history of paying its debts on time. In fact, the United States has never defaulted on its debt.
Return security is a general term that can refer to any type of investment that is expected to generate a return. This could include stocks, bonds, mutual funds, or other types of investments.
Issued security is a term that is used to describe a security that has been issued by a company or government. This could include stocks, bonds, or other types of securities.
In conclusion, treasury bonds are considered to be the safest type of investment because they are backed by the full faith and credit of the United States government.