______ metrics show the number of customers exposed to the ad, as well as the total number of exposures.

The correct answer is Reach and frequency, as these metrics specifically provide insights into the number of unique customers who have been exposed to an ad (reach) and the total number of times the ad has been shown to those customers (frequency). Understanding reach and frequency is crucial for advertisers, as it helps them gauge the effectiveness of their campaigns in terms of audience exposure and engagement. This information allows brands to assess how well their ads are performing and to make informed decisions regarding budget allocation and campaign optimization. In contrast, viewability focuses on whether an ad is actually seen, while new-to-brand metrics evaluate the impact of campaigns on acquiring first-time customers, rather than measuring exposure directly.