8. When buying a treasury bill, an investor is certain that interest and principal payments will be made as promised. This means that treasury bills are a. secured b. risk free c. has no default risk d. a and b are correct e. b and care correct 9. Duration measures the sensitivity of percentage changes in the bond's price to chang in its yield. a false b. true 10. The Modified Duration is a modification to the (Macaulay) duration measure so th more accurately describes the relationship between proportional changes in a bond price and actual changes in its yield. a. false b. true 11. Portfolio managers attempt to produce a positive alpha by a. market timing b. incorporating stocks that outperform the market in the portfolio c. a and b are correct d. none of the above 12. In an S&P credit rating system, a bond with ratings below BBB-is considere a. noninvestment grade b. or speculative c. a junk bond d. all of the above