What is the primary purpose of Google Cloud IAM?

Correct answer: Control who has access to what resources through role-based access control

Option B is correct because Google Cloud Identity and Access Management (IAM) is the service that controls who, meaning which principals such as users, groups, or service accounts, can take what actions on which Google Cloud resources, using a role-based access control model with predefined and custom roles. Option A is wrong because managing virtual machines is the function of Google Compute Engine; IAM may govern who can manage VMs, but IAM itself is not a VM management service. Option C is wrong because monitoring performance is the domain of Google Cloud Monitoring (formerly Stackdriver), which collects metrics, logs, and traces and is a separate service from IAM. Option D is wrong because storing data is handled by services such as Cloud Storage, Bigtable, or BigQuery; IAM controls access to those services but does not itself store data.