Answer: Update the existing Kubernetes Engine cluster with the following command: gcloud alpha container clusters update mycluster - -enable- autoscaling - -min-nodes=1 - -max-nodes=10

The question asks to enable autoscaling on an existing (running) GKE cluster to dynamically scale based on application demand. Option C is correct because it uses the 'update' command to enable autoscaling on the existing cluster, setting appropriate min and max node limits (1-10), which avoids downtime and redeployment. The community consensus strongly supports C (100% in answers_community, with high upvotes on comments confirming C). While the command in C uses 'alpha' (which may be outdated in current versions), it was historically correct and aligns with the principle of updating an existing cluster. Option A is incorrect as it manually resizes the cluster to a fixed size (10 nodes), not enabling autoscaling. Option B is incorrect because adding tags does not enable autoscaling; it is unrelated to GKE's autoscaling mechanism. Option D is incorrect as it creates a new cluster, which is unnecessary and disruptive for an existing running cluster.

Author: LeetQuiz Editorial Team