This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Anatomy
TRUE regarding presentation of primary T.B is 
Select and explain. 
A. Bilateral pleural effusion with negative Tuberculin test, B. Unilateral hilar lymphadenopathy, C. Sustained chronic pyrexia, D. Bilateral pleural effusion with postive Tuberculin test
B: Unilateral hilar lymphadenopathy
Answer: B: Unilateral hilar lymphadenopathy 
Explanation: Because most inspired air is distributed to the middle and lower lung zones, these areas are most commonly involved in primary TB. The lesion forming after initial infection (Ghon focus) is usually peripheral and accompanied by transient hilar or paratracheal lymphadenopathy, which may or may not be visible on standard chest radiography. Ref Harrison 19th edition pg 1108