To enable Security defaults for contoso.com, you should first sign in to the Azure portal as a security administrator, Conditional Access administrator, or global administrator. Then, browse to Azure Active Directory > Properties and select Manage security defaults. Set the Enable security defaults toggle to Yes and select Save.
After that, you can assign Admin1 the Identity Administrator role for Au1 to enable them to manage security defaults for the tenant.
https://practical365.com/what-are-azure-ad-security-defaults-and-should-you-use-them/

Explanation:

Explanation:

Reference:
https://docs.microsoft.com/en-us/azure/role-based-access-control/role-assignments-portal
https://docs.microsoft.com/en-us/azure/active-directory/roles/permissions-reference
Topic 2, Contoso, LtdOverview
Contoso, Ltd is a consulting company that has a main office in Montreal offices in London and Seattle.
Contoso has a partnership with a company named Fabrikam, Inc Fabcricam has an Azure Active Diretory (Azure AD) tenant named fabrikam.com.
Existing Environment
The on-premises network of Contoso contains an Active Directory domain named contos.com. The domain contains an organizational unit (OU) named Contoso_Resources. The Contoso_Resoureces OU contains all users and computers.
The Contoso.com Active Directory domain contains the users shown in the following table.

Microsoft 365/Azure Environment
Contoso has an Azure AD tenant named Contoso.com that has the following associated licenses:
Microsoft Office 365 Enterprise E5
Enterprise Mobility + Security
Windows 10 Enterprise E5
Project Plan 3
Azure AD Connect is configured between azure AD and Active Directory Domain Serverless (AD DS). Only the Contoso Resources OU is synced.
Helpdesk administrators routinely use the Microsoft 365 admin center to manage user settings.
User administrators currently use the Microsoft 365 admin center to manually assign licenses, All user have all licenses assigned besides following exception:
The users in the London office have the Microsoft 365 admin center to manually assign licenses. All user have licenses assigned besides the following exceptions:
The users in the London office have the Microsoft 365 Phone System License unassigned.
The users in the Seattle office have the Yammer Enterprise License unassigned.
Security defaults are disabled for Contoso.com.
Contoso uses Azure AD Privileged identity Management (PIM) to project administrator roles.
Problem Statements
Contoso identifies the following issues:
* Currently, all the helpdesk administrators can manage user licenses throughout the entire Microsoft 365 tenant.
* The user administrators report that it is tedious to manually configure the different license requirements for each Contoso office.
* The helpdesk administrators spend too much time provisioning internal and guest access to the required Microsoft 365 services and apps.
* Currently, the helpdesk administrators can perform tasks by using the: User administrator role without justification or approval.
* When the Logs node is selected in Azure AD, an error message appears stating that Log Analytics integration is not enabled.
Planned Changes
Contoso plans to implement the following changes.
Implement self-service password reset (SSPR). Analyze Azure audit activity logs by using Azure Monitor- Simplify license allocation for new users added to the tenant. Collaborate with the users at Fabrikam on a joint marketing campaign. Configure the User administrator role to require justification and approval to activate.
Implement a custom line-of-business Azure web app named App1. App1 will be accessible from the internet and authenticated by using Azure AD accounts.
For new users in the marketing department, implement an automated approval workflow to provide access to a Microsoft SharePoint Online site, group, and app.
Contoso plans to acquire a company named Corporation. One hundred new A Datum users will be created in an Active Directory OU named Adatum. The users will be located in London and Seattle.
Technical Requirements
Contoso identifies the following technical requirements:
* AH users must be synced from AD DS to the contoso.com Azure AD tenant.
* App1 must have a redirect URI pointed to https://contoso.com/auth-response.
* License allocation for new users must be assigned automatically based on the location of the user.
* Fabrikam users must have access to the marketing department's SharePoint site for a maximum of 90 days.
* Administrative actions performed in Azure AD must be audited. Audit logs must be retained for one year.
* The helpdesk administrators must be able to manage licenses for only the users in their respective office.
* Users must be forced to change their password if there is a probability that the users' identity was compromised.