Which of these are acetotropic methanogens?

• A. Methanoculleus thermophilicus, Methanosphaera stadtmanii
• B. Methanosarcina thermophila, Methanosaeta concilii
• C. Methanosarcina thermophila, Methanosphaera stadtmanii
• D. Methanoculleus thermophilicus, Methanosarcina thermophila