Was jefferson correct in believing the voice of the common people would preserver liberty?

It depends on how you look at it.  Because of the situation in the late 1700s, people like Jefferson were very afraid that the government would have too much power, like what happened in Great Britain during the American Revolution.  

So it makes sense that Jefferson believed that the only way to preserve liberty was in the voice of the common man.  That's why it was emphasized when the Constitution was created that a Bill of Rights should be written to help give the common people protected rights and preserve their most important freedoms.  

The First Amendment for example, does preserve freedoms for the common people in the United States and is very important in understanding how these individual rights gave liberty and freedom to people back in the late 1700s as well as throughout history.  

your answer would be (b)