This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory, Subject name: Medicine
True regarding presentation of primary T.B. is : 
Select and explain. 
A. B/L pleural effusion with negative Tuberculin test., B. U/L hilar lymphadenopathy, C. Sustained chronic pyrexia, D. B/L pelural effusion with positive tuberculin test.
B: U/L hilar lymphadenopathy
Answer: B: U/L hilar lymphadenopathy 
Explanation: Ans is 'b' ie Unilateral hilar lymphadenopathy Pleural effusion occurs in T.B. as a result of penetration of a few tubercle bacilli into the pleural space from an adjacent subpleural focus. Therefore pleural effusion is usually unilateral because the lesion in T.B. is also unilateral (so the tubercle bacilli will reach the pleura of the involved lung only)Tuberculosis is invariably accompanied by involvement of the hilar or mediastinal lymph nodes.