Which 8D Methodology discipline covers this action?

Avaya Support personnel report a case, including root cause and resolution, in the Knowledge Base.

Which 8D Methodology discipline covers this action?

A. D8
B. D7

C. D6

D. D5

Reference: http://www.brooks.com/my-brooks/suppliers/~/media/Files/Suppliers/Documents/5_Why_Root_Cause_Corrective_Actions.pdf