Configure single sign-on in the Google domain
Single sign-on: Whenever a user needs to authenticate, Google Cloud delegates the authentication to Active Directory by using the Security Assertion Markup Language (SAML) protocol. This delegation ensures that only Active Directory manages user credentials and that any applicable policies or multi-factor authentication (MFA) mechanisms are being enforced. For a sign-on to succeed.

https://cloud.google.com/architecture/identity/federating-gcp-with-active-directory-introduction Reference Link- https://cloud.google.com/architecture/identity/single-sign-on

Spanner, Cloud SQL, BigQuery
Spanner- Cloud Spanner is a fully managed, mission-critical, relational database service that offers transactional consistency at global scale, automatic, synchronous replication for high availability, and support for two SQL Google Standard SQL and PostgreSQL.
Cloud SQL- Cloud SQL is a fully-managed database service that helps you set up, maintain, manage, and administer your relational databases on Google Cloud Platform.
BigQuery- Google BigQuery is a cloud-based Architecture and provides exceptional performance as it can auto-scale up and down based on the data load and performs data analysis efficiently. On the other hand, SQL Server is based on client-server architecture and has fixed performance throughout unless the user scales it manually.

Autoscaling is supported in both Flexible and Standard environments. Flexible Environment does run a Docker container that includes a custom runtime or source code written in other programming languages.
Reference link - https://cloud.google.com/appengine/docs/the-appengine-environments

Option A is Correct- BigQuery Flex Slots for cyclical workloads that require extra capacity, or for workloads that need to process a lot of data in a short time, and so would be less expensive to run using reserved slots for a short time.

Lending DocAI is a pre-packaged AI solution that speeds "up the mortgage workflow processes to easily process loans and automate document data capture, while ensuring the accuracy and breadth of different documents (e.g., tax statements and asset documents)."
https://cloud.google.com/solutions/lending-doc-ai