What can you do by creating a separate campaign that's targeted only to the display network?

When you create a separate campaign that's targeted only to the display network you are able to have a direct focus on one specific aspect of advertising. You are able to allocate your resources better and prioritize where you want most of your funds to go and focus on just that network. 

It would be choice b (randomly selected)

The advantage of administering personality tests on employees is that it will allow the employer to know the mindset and personality of the employee. this will allow the employer to at least have an idea as to how the employee works and how his attitude in the workplace. the disadvantage is that it may make the employee a little anxious as to whether he would meet the personality requirements of the employer and whether he would be able to retain the job or not.