Statements I and II accurately describe the characteristics of bonds. The debt maturity is indeed the date when the bond issuers fulfill their obligation as per the bond indenture. This obligation typically involves the repayment of the bond principal and any outstanding interest or coupons. The bond maturity date, as stated in Statement II, is the day when the bond principal and the remaining coupon are paid. This is the date when the bond issuer has fully satisfied its obligations to the bondholders. Therefore, both these statements are correct and accurately reflect the dynamics of bonds in the financial market.

Choice B is incorrect. While Statement II is correct, Statement III is not. The maturity date of a bond issue can be changed under certain circumstances, such as when the issuer calls the bond before its original maturity date or when there are provisions for extending the maturity date in the bond indenture.

Choice C is incorrect. Although Statement I correctly describes debt maturity, Statement III does not accurately reflect the dynamics of bonds in financial markets. As mentioned above, there are situations where a bond's maturity date can be altered.

Choice D is incorrect. This choice incorrectly assumes that all three statements are accurate descriptions of bonds' characteristics and dynamics in financial markets. However, as explained above, Statement III does not hold true under all circumstances.