Answer:
The answer to this question is option B which is "Disable the health check for the instance group. Add his SSH key to the project-wide SSH keys"
Step-by-step explanation:
Option A is not correct because to connect with SSH, IAM role is not needed.
Option C is incorrect because performing a rolling restart would mean you think the problem is with Google Compute engine
Option B is correct because on Google compute engine, there are automatic health checks which leads to a restart of your instance anytime it fails. Disabling the health check will stop restarting of your instance.