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.

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

You must know that during electrolysis the water decomposes to make hydrogen and oxygen gases in the ratio 2:1 by volume, respectively. As 2H₂O (l) + Electric current → 2H₂(g) + O₂ (g)