This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oxygen dependent bacterial killing, Subject name: Pathology
[{'content': 'The main feature of chemotaxis is: \nSelect and explain. \nA. Increased random movement of neutrophils, B. Increase adhesiveness to intima, C. Increased phagocytosis, D. Unidirectional locomotion of the neutrophils', 'role': 'user'}, {'content': 'Answer: D \nExplanation: After exiting the circulation, leukocytes move in the tissues toward the site of injury by a process called chemotaxis, which is defined as locomotion along a chemical gradient. Both exogenous and endogenous substances can act as chemo-attractants.', 'role': 'assistant'}]