A 56 year old electrician presents to his GP with a six month history of gradually increasing shortness of breath. He is an ex-smoker (30 pack years) but he has no other respiratory symptoms. After examining his chest, the GP requests a chest x ray. Which one of the following statements about this chest x ray is correct?
A) There is collapse of the entire left lung
B) There is a fluid meniscus in the left upper zone
C) The most likely cause of this appearance is heart failure
D) The cause of this abnormality is visualised on this x ray