Final answer:
The best practice for using Oracle CPQ Cloud WebServices is to store XML templates in the file manager and utilize them from within BML, as it provides a maintainable and secure approach.
Step-by-step explanation:
The recommended option for using Oracle CPQ Cloud (formerly BigMachines) WebServices is B. Store XML templates in file manager and use them from within BML (BigMachines Language).
This method allows for consistent and maintainable code, enabling users to easily update and manage the XML payloads that are sent in WebServices calls. Hard coding URLs (A) is typically discouraged as it makes the code less flexible and harder to maintain, especially if the URLs change.
Making WebServices calls directly from the rules (C) can lead to performance issues and is not considered a best practice. Lastly, saving and reusing session IDs (D) is generally not recommended due to security concerns and the potential for session expiration, which can cause errors in the application.