Which Apple service allows users to store their data in the cloud?

iCloud is the service provided by Apple that enables users to store their data in the cloud. It offers a variety of features that allow for seamless synchronization and backup of documents, photos, music, and more across all Apple devices. When users utilize iCloud, they can access their stored data from multiple devices—such as iPhones, iPads, and Macs—ensuring that their information is always up-to-date and retrievable from anywhere with an internet connection. iCloud also supports additional functionalities like sharing files with other users and managing device backups, further enhancing its role as a comprehensive cloud storage solution.

The other options do not serve the same purpose as iCloud. Apple Drive, for instance, is not an official service provided by Apple; users might confuse it with iCloud Drive, which is a component of iCloud for file storage. iTunes is primarily a media management and purchasing platform, while the App Store is focused on software and app distribution, making none of these alternatives a suitable choice for cloud-based data storage.