Implement an IPsec Cloud VPN to a VPC, restrict tunnel reachability to specific on-prem subnets, and your on-prem device cannot run BGP. Which routing option should you choose?

The correct option is Policy-based VPN with a custom local traffic selector. This is because Policy-based VPNs are used when BGP cannot be run on the on-premises device, as they rely on static routes or policy-based routing. To restrict tunnel reachability to specific on-prem subnets, a custom local traffic selector is required. This selector explicitly defines the on-premises IP ranges that can communicate through the VPN tunnel. Dynamic routing with Cloud Router is incorrect because the on-premises device cannot run BGP. Route-based VPN using default traffic selectors is incorrect because it typically uses 0.0.0.0/0 as traffic selectors, which would not restrict reachability to specific on-prem subnets. Policy-based VPN with the default local traffic selector is incorrect because the default selector is usually 0.0.0.0/0, which would allow all traffic and not restrict to specific subnets.