You Are a Consultant for David's Company and He's Asked

You are a consultant for David's company and he's asked you to help him create a Google AdWords for his company's products. You and David develop a keyword list and the ad has now been running for two weeks. David wants to edit the keyword list, but you tell him the ads should run longer before editing the list. How long does Google recommend the keyword list and ads run, before evaluating their performance?

A) 30 days
B) You can edit the ads immediately.
C) 21 days
D) 14 days