A is the correct answer,
Granting private nodes outbound internet access
To provide outbound internet access for your private nodes, such as to pull images from an external registry, use Cloud NAT to create and configure a Cloud Router. Cloud NAT lets private clusters establish outbound connections over the internet to send and receive packets.
The Cloud Router allows all your nodes in the region to use Cloud NAT for all primary and alias IP ranges. It also automatically allocates the external IP addresses for the NAT gateway.
For instructions to create and configure a Cloud Router, refer to Create a Cloud NAT configuration using Cloud Router in the Cloud NAT documentation.
https://cloud.google.com/kubernetes-engine/docs/how-to/private-clusters#private-nodes-outbound