Cortadryl, an Anti-Itching Cream, Advertises on the Internet

Cortadryl, an anti-itching cream, advertises on the Internet. To target its advertising, Cortadryl has its banner ads appear when a user types in the words "itchy," "scratching," "hives," or "mosquitoes" in the search engine. Cortadryl has most likely made a:

A) request for ad responses.
B) click-through request.
C) keyword purchase.
D) word-search responsive device.
E) base banner purchase.