Google recommend groups and roles/browser provides Read access to browse the hierarchy for a project, including the folder, organization, and Cloud IAM policy. This role doesn't include permission to view resources in the project.
https://cloud.google.com/iam/docs/understanding-roles

We recommend collecting users with the same responsibilities into groups and assigning IAM roles to the groups rather than to individual users. For example, you can create a "data scientist" group and assign appropriate roles to enable interaction with BigQuery and Cloud Storage. When a new data scientist joins your team, you can simply add them to the group and they will inherit the defined permissions. You can create and manage groups through the Admin Console.
https://cloud.google.com/compute/docs/instances/managing-instance-access

You must enable binary logging to use point-in-time recovery. Enabling binary logging causes a slight reduction in write performance.
https://cloud.google.com/sql/docs/mysql/backup-recovery/backups

On-demand pricing
Under on-demand pricing, BigQuery charges for queries by using one metric: the number of bytes processed (also referred to as bytes read). You are charged for the number of bytes processed whether the data is stored in BigQuery or in an external data source such as Cloud Storage, Drive, or Cloud Bigtable. On-demand pricing is based solely on usage.
https://cloud.google.com/bigquery/pricing#on_demand_pricing

A is not correct because BigQuery is not a transactional system.
B is correct because Cloud SQL is a relational and transactional database in the list.
C Is correct because Spanner is a relational and transactional database in the list.
D is not correct because Cloud Bigtable provides transactional support but it's not relational.
E Is not correct because Datastore is not a relational data storage system.