A customer views an ad, clicks on the ad, and then makes a purchase. What type of activity is this?

The correct answer is Post-click conversion because this activity involves the customer first viewing the ad, then clicking on it, and finally making a purchase. A post-click conversion specifically refers to a conversion that occurs after the user has clicked on the ad, indicating that the conversion (purchase) is attributed to the user's click on the ad. This differentiates it from post-view conversions, where the conversion occurs after simply viewing the ad without any click. Therefore, since the purchase happened following a click, it is classified as a post-click conversion.