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': 'In dividing cells, spindle is formed by : \nSelect and explain. \nA. Ubiquitin, B. Tubulin, C. Laminin, D. Keratin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: B i.e. Tubulin', 'role': 'assistant'}]