Oxygen from the atmosphere reaches the mammalian blood stream through one of the path indicated below. Indicate the correct path, a = mouth, b = trachea, c = bronchiole, d = nostril, e = bronchus, f = alveoli

• A.a → b → e → f → d
• B.b → d → f → e → c
• C.d → b → e → c → f
• D.b → a → f → e → c
• E.f → e → c → d → c