This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Immune system, Subject name: Medicine
[{'content': 'Diagnosis of X linked agammaglobuliflem should be suspected if- \nSelect and explain. \nA. Absent tonsils and no palpable lymph nodes on physical examination, B. Female Sex, C. High Isohemagglutinins titers, D. Low CD 3', 'role': 'user'}, {'content': "Answer: A \nExplanation: X-linked disorders Males have only one X chromosome; consequently, a daughter always inherits her father's X chromosome in addition to one of her mother's two X chromosomes. A son inherits the Y chromosome from his father and one maternal X chromosome. Thus, the characteristic features of X-linked inheritance are (1) the absence of father-to-son transmission, and (2) the fact that all daughters of an affected male are obligate carriers of the mutant allele", 'role': 'assistant'}]