An advertiser sells textbooks to nearby college students and only wants to target its ad to people on Pinterest aged 18-24. Which targeting option should it use to reach this audience?

The correct answer is Demographic targeting. This option allows advertisers to reach users based on characteristics like age, gender, and location. Since the advertiser specifically wants to target people aged 18-24, demographic targeting is the most direct and effective method. Interest targeting would reach users based on their expressed interests on Pinterest, which might include students but isn't precise enough for an age-specific group. Actalike (lookalike) targeting finds new users who resemble existing customers, which doesn't guarantee the desired age range. Keyword targeting delivers ads based on search terms or content, which also wouldn't isolate users by age.