How do you differentiate between which one is the anode and cathode inside a voltaic cell when given a voltaic cell diagram?

Not a  mixture of two common elements that can be separated by physical means.

A. is your answer.  hope this  

It's called the falling actionwrong subject by the way

Remember that rust prevented by placing a sacrificial electrode in electrical contact with the iron. the sacrificial electrode must be composed of a metal that  oxidizes  more easily than iron (that is, it must be below iron in table 18.1).