The answer is b
Yada yada yada
The communist Manifesto was written by Karl Marx and by Friedrich Engels- Engels is the person you were looking for!
There is some discussion about the role of both authors in writing it, and some people suggest that Karl Marx did most of the work, with Engels having a smaller role.
True. Cognitive dissonance occurs when two conflicting thoughts/emotions come in contact with one another so the consumer buying something and knowing they shouldn't have bought it forces them to try and justify their need for the object they purchased so they don't feel that dissonance anymore.
I hope I was able to help. Best of luck!