This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Serum lacks the fibrinogen and the following clotting factors: \nSelect and explain. \nA. 2,5,8, B. 2,5,8,9, C. 8,9, D. 8,9,10', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Clot\xa0Retraction\xa0and\xa0Expression\xa0of\xa0Serum\nWithin\xa0a few minutes after a clot is formed, it begins to contract and\xa0usually\xa0expresses\xa0most\xa0of\xa0the\xa0fluid\xa0from\xa0the\xa0clot within\xa020\xa0to\xa060\xa0minutes.\xa0The\xa0fluid\xa0expressed\xa0is\xa0called serum\xa0because\xa0all\xa0its\xa0fibrinogen\xa0and\xa0most\xa0of\xa0the\xa0other clotting\xa0factors\xa0have\xa0been\xa0removed;\xa0in\xa0this\xa0way,\xa0serum differs from plasma. Serum cannot clot because it lacks these factors.\nSerum lacks the ﬁbrinogen and the clotting factors II,V,VIII.', 'role': 'assistant'}]