We need to ensure the global capacity remains intact, for that reason we need to establish maxUnavailable to 0. On the other hand, we need to ensure new instances can be created. We do that by establishing the maxSurge to 1.
Option C is more expensive and more difficult to set up and option D won't meet requirements since it won't keep global capacity intact.
https://cloud.google.com/compute/docs/instance-groups/rolling-out-updates-to-managed- instance-groups#options

If for any reason VM crashes autoscaling set as OFF wont spin another instance in its place which would defeat the purpose of always running VM(tough there will be some disruption) as -- Max-num-Instance is set to 1.
There is no mention of auto-healing is set or not which is disable by default.
B - Incorrect - Does not fit the requirement because AFTER the deletion of the instance, no other instance was created.

When you install SDK using apt Cloud SDK Component Manager is disabled and you need to install extra packages again using apt.
https://cloud.google.com/sdk/docs/components#managing_cloud_sdk_components Note: These instructions will not work if you have installed Cloud SDK using a package manager such as APT or yum because Cloud SDK Component Manager is disabled when using that method of installation.

The Owner, Editor, and Viewer primitive roles include the BigQuery Admin (roles/bigquery.dataOwner), BigQuery Data Editor (roles/bigquery.dataEditor), and BigQuery Data Viewer (roles/bigquery.dataViewer) roles, respectively. This means the Owner, Editor, and Viewer primitive roles have BigQuery access as defined for the respective BigQuery roles.
Reference: https://cloud.google.com/bigquery/docs/access-control

Cloud SDK comes with a default configuration. To create multiple configurations, use gcloud config configurations create, and gcloud config configurations activate to switch between them.
https://cloud.google.com/sdk/gcloud/reference/config/set