How should Smart Folders be identified and recognized?

How should Smart Folders be identified and recognized?
A . Smart Folders should be recognized by their type smf:smartFolder
B . Smart Folders should be recognized by parent-child type used smf:contains
C . Smart Folders should be recognized by their aspect smf:smartFolder
D . Smart Folders should be recognized by the special node reference used.
E . Smart Folders cannot be recognized as they are not different from any other cm:folder.

Answer: D

Explanation:

References: https://docs.alfresco.com/6.0/references/sf-tech-faqs.html