Question

extends to a height of 50 km above the troposphere
We communications are possible due to the presence of
The percentage of oxygen in the atmosphere is
The main source of heat received by the earth is
while that of nitrogen​

Answer 1

Answer:

1. Stratosphere

2. Radio active waves

3. 20.9 % or 21%

4. Sun

5. 72%

I think you asked the percentage of nitrogen in the last question.

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Answer 2

• First's answer is stratosphere
• Ionosphere which is a part of Thermosphere is the second question's answer
• 21% oxygen in atmosphere, Nitrogen 78%
• Sun is the main source of heat received by the earth