IFRS vs US GAAP treatment of marketable securities

Hi guys!

I’ve been doing the Mock exams and came across a question about the difference between IFRS and GAAP treatment of available-for-sale securities. The question states: Listed debt securities owned by a company, for which the company intends to collect interest payments and sell the securities, must be carried at fair value with gains and losses reported as other comprehensive incomes under -
A. IFRS only
B. U.S GAAP only
C. Both GAAP and IFRS

My original answer was C but the mock answer sheet is saying its B. I’m looking through the relevant section in the book and it appears that the treatment of available for sale securities is VERY similar between IFRS and GAAP. Can someone help explain why it’s only US GAAP? Thank you!