Explanation:

A) Named Credential
A Named Credential in Salesforce is used to securely store and manage authentication details for external service callouts, including the callout URL and authentication settings (e.g., OAuth, Basic Authentication). In the context of Salesforce Media Cloud integrating with Google Ad Manager, a Named Credential is the appropriate component to specify the callout URL for the Google Ad Manager API endpoint (e.g., https://ads.google.com/apis/ads/publisher).

Named Credentials simplify the process by:

Storing the endpoint URL for the Google Ad Manager API.
Managing authentication details, such as OAuth 2.0 tokens or API keys, required for secure communication.
Allowing Media Cloud’s integration processes (e.g., OmniStudio Integration Procedures or Apex callouts) to reference the Named Credential without hardcoding sensitive information.

For Cloud Kicks, the consultant would create a Named Credential to define the Google Ad Manager API URL and configure authentication (likely OAuth 2.0, given Google’s API standards), enabling Media Cloud to send order data (e.g., ad campaign details from Contract Line Items) securely to Google Ad Manager. This ensures seamless integration and compliance with Salesforce security best practices.

Incorrect Options:

B) Connected App
A Connected App is used to integrate external applications with Salesforce, allowing them to access Salesforce data via APIs (e.g., a third-party app accessing Salesforce via OAuth). In this scenario, Cloud Kicks needs to send data from Salesforce Media Cloud to Google Ad Manager, not the other way around. A Connected App would be relevant if Google Ad Manager were initiating access to Salesforce data, but for specifying a callout URL to an external service, a Connected App is not required. Instead, a Named Credential handles the outbound integration, making this option incorrect.

C) Custom Metadata
Custom Metadata is used to store customizable, application-specific metadata that can be deployed and queried, such as configuration settings or mappings. While Custom Metadata could theoretically store a URL as a text field, it is not the standard or secure method for specifying callout URLs in Salesforce. Custom Metadata does not inherently support authentication management or secure callout handling, which are critical for integrating with Google Ad Manager. Named Credentials are specifically designed for this purpose, providing both URL specification and secure authentication, so this option is incorrect.

D) Auth. Provider
An Auth. Provider (Authentication Provider) is used to configure single sign-on (SSO) or OAuth-based authentication for external identity providers (e.g., Google, Salesforce) to allow users to log into Salesforce or enable external apps to authenticate with Salesforce. While an Auth. Provider might be used in conjunction with a Named Credential to define OAuth settings for Google Ad Manager, it does not directly specify the callout URL. The Named Credential encapsulates both the URL and the authentication configuration (referencing the Auth. Provider if needed), making the Named Credential the primary component required, not the Auth. Provider alone. This option is incorrect because it does not fully address the requirement of specifying the callout URL.

Reference:
Salesforce Help: “Named Credentials”
Salesforce Media Cloud Documentation: “Google Ad Manager Integration”
Trailhead: “Media Cloud Basics” module
Salesforce Developer Guide: “External Services and Named Credentials”