To pursue its goal, the fund invests in U.S. government securities, such as U.S. Treasury bills and notes other obligations that are issued by the U.S. government, its agencies or instrumentalities, including obligations that are not fully guaranteed by the U.S. Treasury, such as those issued by the Federal National Mortgage Association (Fannie Mae), the Federal Home Loan Mortgage Corporation (Freddie Mac) and the Federal Home Loan Banks, repurchase agreements that are collateralized fully by cash and/or U.S. government securities.