What is the primary purpose of Google Cloud Directory Sync?

The primary purpose of Google Cloud Directory Sync is to sync users and group memberships in Cloud Identity. This tool facilitates the integration of on-premises directory services, such as Microsoft Active Directory, with Cloud Identity. By ensuring that users and their associated groups are consistently synchronized, organizations can effectively manage access and permissions in Google Cloud services. This synchronization is crucial for maintaining a coherent identity management strategy, enabling seamless user experience across various applications and services while ensuring security and compliance.

The other choices do not align with the core function of Google Cloud Directory Sync. For example, synchronizing cloud applications and backing up data between cloud services involve different processes and tools aimed at application management and data storage, rather than identity synchronization. Automating DNS management also pertains to managing domain name systems and doesn't involve user and group management directly. Thus, B accurately identifies the primary role of Google Cloud Directory Sync in the context of Cloud Identity.