In which layer of Earth's atmosphere does outer space begin..? A. ) Stratosphere
B. ) Mesosphere
C. ) Thermosphere
D. ) Troposphere

Please post a real answer.

Option C

Explanation:

Because of how low the air density is, most consider it as entering outer space when you enter into the "Thermosphere" or option C. The Thermosphere is approximately 800 kilometres in the sky right above the Mesosphere and the Stratosphere which most fighter jets maximum height is.

Hope this helps.