Final answer:
An advertiser can provide up to four ad descriptions for responsive search ads. This flexibility allows for a more targeted approach to potential customers based on the search queries they use. The correct option is b.
Step-by-step explanation:
The maximum number of ad descriptions an advertiser can provide for their responsive search ads is four (4).
This allows the ad platform's algorithms to mix and match various headlines and descriptions to create an ad that is most likely to perform well based on the search query and other factors. Responsive search ads are designed to be flexible and optimize your ad content to better match potential customers' searches. The correct option is b.