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.

Metals placed below the hydrogen in reactivity series, will not give H₂(g) with water (H₂O). Decreasing order of reactivity of metals is Na > Mg > Zn > Cu

Class 10 Science Terminal Exams MCQ Solutions Class X Science MCQ Extra Questions Answers 10th Science Terminal Exam Based MCQ Extra Questions Class 10th Science Session 2022-23

As you know that the thickness of atmosphere is low, at very high altitude. So, there are less number of particles present for scattering. Therefore, the sky appears dark to the passengers.