You must know that alveoli play a crucial role of respiration. It has a large surface area with very thin walls which is richly supplied with blood vessels.

Copper gets a green coating due to the formation of a mixture of copper carbonate (CuCO₃) and copper hydroxide when it reacts with carbon dioxide gas and the moisture present in air. This is called tarnishing of copper.

Class 9 Science Terminal Exams MCQ Solutions Class IX Science MCQ Extra Questions Answers 9th Science Terminal Exam Based MCQ Extra Questions Class 9th Science Session 2022-23

Class 9 Science Terminal Exams MCQ Solutions Class 9th Science Session 2022-23 9th Science Terminal Exam Based MCQ Extra Questions Class IX Science MCQ Extra Questions Answers