You must monitor resources across multiple projects and consolidate metrics into a single Stackdriver Monitoring dashboard. What should you do?

The correct approach is to create a single Stackdriver Monitoring account (now called Cloud Monitoring) and link all projects to it. This allows you to view and manage metrics, logs, and traces from multiple projects within a single console, simplifying monitoring and dashboard creation. This is the standard and most efficient way to achieve centralized monitoring across projects in Google Cloud. Using Shared VPC is for network connectivity, not for consolidating monitoring data. Creating a Stackdriver account per project and managing service accounts for cross-project access is overly complex and unnecessary, as Cloud Monitoring is designed for multi-project scope. Creating a Stackdriver Group is for organizing resources within a project or across linked projects, but it doesn't establish the initial cross-project monitoring linkage itself.