Explanation

Scenario: Authenticate database users by using Active Directory credentials.
The configuration steps include the following procedures to configure and use Azure Active Directory authentication.
Create and populate Azure AD.
Optional: Associate or change the active directory that is currently associated with your Azure Subscription.
Create an Azure Active Directory administrator. (Step 1)
Configure your client computers.
Create contained database users in your database mapped to Azure AD identities. (Step 2) Connect to your database by using Azure AD identities. (Step 3) Reference:
https://docs.microsoft.com/en-us/azure/azure-sql/database/authentication-aad-overview

Explanation
B: Dynamic Thresholds continuously learns the data of the metric series and tries to model it using a set of algorithms and methods. It detects patterns in the data such as seasonality (Hourly / Daily / Weekly), and is able to handle noisy metrics (such as machine CPU or memory) as well as metrics with low dispersion (such as availability and error rate).
D: Alert threshold sensitivity is a high-level concept that controls the amount of deviation from metric behavior required to trigger an alert.
Low - The thresholds will be loose with more distance from metric series pattern. An alert rule will only trigger on large deviations, resulting in fewer alerts.
Reference:
https://docs.microsoft.com/en-us/azure/azure-monitor/platform/alerts-dynamic-thresholds

Explanation
The Plan Comparison menu option allows side-by-side comparison of two different execution plans, for easier identification of similarities and changes that explain the different behaviors for all the reasons stated above.
This option can compare between:
Two previously saved execution plan files (.sqlplan extension).
One active execution plan and one previously saved query execution plan.
Two selected query plans in Query Store.

Explanation
Graphical user interface, text, application, email Description automatically generated

Box 1: Key Lookup
The Key Lookup cost is 99% so that is the performance bottleneck.
Box 2: nonclustered index
The key lookup on the clustered index is used because the nonclustered index does not include the required columns to resolve the query. If you add the required columns to the nonclustered index, the key lookup will not be required.