Assertion (A): Alveoli contain an extensive  network of blood vessels.  

Reason (R): Alveoli is the site where exchange of  gases occurs.  




  • The alveoli of lungs are richly supplied with blood
  •  Alveoli are the sites where exchange of gases (O 2 and CO 2 ) occurs between blood and the atmosphere. 
  • The alveoli increase the surface area for this exchange of gases and hence have an extensive network of blood vessels to maximise efficiency.



  • The assertion is True
  • The reason is True

The reason is the correct explanation of the assertion

Exchange of gases at alveoli-01.jpg

So, the correct option is (a) 

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo