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: Pharmacology
[{'content': 'The following statements regarding histamine are true, except: \nSelect and explain. \nA. It can be used as a positive control injection during allergy skin testing, B. In the dermis, it evokes pain and sometimes itching, C. Bronchospasm is induced by histamine by  blockage of H2 receptors, D. It tends to dilate larger blood vessels', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Histamine characteristically causes dilation of the finer blood\xa0vessels and tends to constrict the larger blood vessels, it is used\xa0as a positive control injection during allergy skin testing. It can\xa0stimulate various nerve endings and in the dermis it evokes pain\xa0and sometimes itching. Contraction of bronchial smooth muscles\xa0is due to activation of H1 receptors and relaxation is due to\xa0activation of H2 receptors. Hence, blockade of H2 receptors can\xa0potentiate histamine-induced bronchospasm.', 'role': 'assistant'}]