Why Is It, According to Dissonance Theory, That We Evaluate

Multiple Choice

Why is it, according to dissonance theory, that we evaluate favorably those goals we've had to suffer for?

A) The goals themselves are valuable; otherwise, we wouldn't go to all that time and trouble.
B) Deep down, people really like to work hard for what they get.
C) We are motivated to justify the time and effort we've spent.
D) Reaching the goal ends our suffering and, thus, is rewarding.