Assume a year ago the US Treasury yield curve was flat at a rate of 4% per year (with annual compounding) and you bought a 30-year US Treasury bond. Today it is flat at a rate of 5% per year (with annual compounding). What rate of return did you earn on your initial investment, if the bond was a 4% coupon bond with $100 face value?
选项：

A:-11.14%;
B:-12.14%;
C:-13.14%;
D:-14.14%