Answer:
Option C) % decrease in cost per click and cost per impression
Step-by-step explanation:
The effectiveness of the program will be proved by the reach that your company will gain through it, measured by social networks reach, new employees, people talking about your company, etc. The % decrease in cost per click is also important, but it will not ensure that your program will succeed, it will just lower the expenses. Therefore, it is not a metric that you should look at when managing an advocate program.