In google adwords, What's one benefit of creating multiple ad groups?

Creating multiple adgroups will help you orgaize on product or services themes. You can add more relevant keywords to the adgroups and thus create more relevant ads. This will also help you identify which adgrup and which keywords are performing better and thus help you in optimizing your campaign. 

Is a Google Ads Fundamentals Certification Exam question.

The correct answer is:  You can break up keywords and ads into related themes

Source, explanation and more answers: https://www.certificationanswers.com/en/whats-one-benefit-of-creating-multiple-ad-groups/

Video explanation: https://www.youtube.com/watch?v=YibyfmK6PPI

Multiple Ad Groups allows you to group ads based on a specific theme or group of words. What this does is makes it easier to manage each ad group and monitor performces of those groups individually.