The answer should be B.
Credibility is important for obvious reasons. Who's going to trust a site that just gets their information from the ether?
Rhetorical questions can make the individuals in an audience feel like they are going through unnecessary pain, which would make them more likely to get the product being advertised.
Logos are... a bit complicated. You can just look that one up.
Hope this helped!
Answer:
My fellow Americans: ask not what your country can do for you—ask what you can do for your country.”
