Nia is the marketer for East Coast Sales. She's the project lead for a new smartphone app that will help customers order products more easily. Thanks to Google's advice, their dev team has incorporated many features to boost conversion numbers. Before rolling out the app, they'd like to perform some testing to determine the effectiveness of the personalization features. Which Google service allows them to test the app's UI and features?

Firebase A/B Testing is the correct choice because it is specifically designed for testing UI and features within mobile applications. It allows marketers to run experiments on different versions of their app to see which performs better in terms of user engagement and conversion goals. Google Analytics 360 is an analytics platform for websites and apps, but it doesn't directly facilitate A/B testing of app features. Web Vitals is a set of metrics for assessing website performance and user experience, not for app feature testing. Test My App is not a recognized Google service for A/B testing mobile app features.