Unlike a bond's value, which can be estimated with more certainty, a stocks value is more difficult to determine. Which of the following best explains why? a$)$ Bonds have guaranteed specific payment amounts, but stocks do not. b$)$ Bonds have a guaranteed rate of return, but stocks do not. c$)$ Bonds have a specific end value $($maturity value$),$ but stocks do not. d$)$ All of the above are correct.