Hi Harry,
thanks for your answer, and I'm not trying to be impolite here, and with all respect but your answer did not seem to actually answer what I was asking (I'm sorry but I couldn't see).
I guess rephrasing: if Scope Statement is an input to a WBS( as shown in page 156 of the 6th edition) why it could not be considered as something that would help build a WBS? and if the PM should consider the possibility of looking for OPAs outside of his company why can't he/she find lessons learned from another company as an input to the WBS, making the explanation for option B also valid for option A.
thanks,