Definition: You are given a question on college biology. You are also given 4 answer options (associated with "A", "B", "C", "D"), out of which only one is correct. You need to answer the question by selecting the correct option. You should only answer with the choice letter, not the whole answer.
Input: A prokaryote that is thermophilic and methanogenic and has isoprenylglycerol ethers in its membrane instead of phospholipids is most likely
(A)a proteobacterium (B)a spirochete (C)a member of the genus Chlamydia (D)an archaeon

D