A parent company uses IFRS and has a subsidiary whose books are maintained following U.S. GAAP. The consolidated financial statements of the parent include the subsidiary's accounts, reported using: 

a. U.S. GAAP 

b. Either IFRS or U.S. GAAP, since both are acceptable 

c. A combination of IFRS and U.S. GAAP, depending on the account 

d. IFRS