Explanation:

In Salesforce B2C Commerce, services are configured using three components:

Service Definition (ID, type, etc.)
Service Profile (timeout, logging, retry rules)
Service Credential (username, password, URL)

While the service credential defines the default URL for the service, sometimes during development or sandbox testing, you need to override that URL without changing the credential itself — e.g., for testing with different environments.
To do this, B2C Commerce provides an Override URL feature in the Service Status area of Business Manager.

📌 How to do it:
Go to Business Manager
→ Administration > Operations > Services
Select the service you want to modify.

In the Service Status section, you'll see:
Override URL checkbox
A URL field
✅ Check the “Override URL” box
📝 Enter the custom URL you want the service to call.
Save the changes.
At runtime, the service will use this override URL instead of the one defined in the credential.

❌ Why the other options are incorrect:
A. Use the service credential URL field
🔴 This is the default place to set the URL, but it is not editable dynamically during runtime or testing without affecting the entire credential.
You cannot switch URLs manually on the fly this way.

C. Use a Site preference dedicated for the service URL
🔴 While this is a flexible custom-built solution, it is not required when the goal is to manually override a URL for a service.
Better suited for dynamically switching URLs via code.

D. Use a Global preference dedicated for the service URL
🔴 Same as C — this is custom and unnecessary here.
The built-in override functionality is the correct tool.

📚 Reference:
Salesforce B2C Commerce Developer Documentation – Services Configuration
SFCC Business Manager path:
Administration > Operations > Services > [Select Service] > Service Status

🧠 Summary:
To manually change a service URL in a sandbox, use the built-in Service Status override feature in Business Manager. This allows you to test different endpoints without editing credentials or custom preferences.