<prompt> A man presented with bilateral crepitations In the base of the lungs and signs of pneumonitis with a history of exposure to pigeon faeces. What is true about this condition?Diagnosis can be made on the basis of historyCT scan is the investigation of choiceChest X-ray will reveal characteristics changesIt is a type 1 hypersensetivity reaction  <response>: Patient may developed hypersensitive pneumonitis. 