What is the best description of how assets and liabilities of a subsidiary are shown in consolidation, when the acquirer bought stock in steps, occurring over several years?

a. They are shown based on the book values on the subsidiarys books

b. They are shown based on fair value as of the latest date stock was acquired, as long as the acquirer has significant influence, adjusted for amortization

c. They are shown based on fair value as of the time the acquirer first obtained significant influence, adjusted for amortization

d. They are shown based on fair value as of the time the acquirer first obtained control, adjusted for amortization