Your company is developing an application that users on their mobile devices will primarily use. The users need to have the ability to authenticate themselves via identity providers through Security Assertion Markup Language 2.0. Which of the following service should be used for user management?

Answer options:

A.AWS STS with IAM
B.AWS Cognito Identity Pools
C.AWS Security Pools
D.AWS IAM Pools

Answer – B
This is also given in the AWS Documentation.
Amazon Cognito supports authentication with identity providers through Security Assertion Markup Language 2.0 (SAML 2.0). You can use an identity provider that supports SAML with Amazon Cognito to provide a simple onboarding flow for your users. Your SAML-supporting identity provider specifies the IAM roles that can be assumed by your users so that different users can be granted different sets of permissions.
Because of what is mentioned in the AWS Documentation, all other options are invalid.
For more information on SAML Identity provider, please refer to the below URL-
https://docs.aws.amazon.com/cognito/latest/developerguide/saml-identity-provider.html