Introduction:
When observing the Earth from a height of six miles in the sky, one of the first things that can be noticed is that the Earth appears round. This observation provides evidence for the shape of our planet and contradicts the notion of a flat Earth.

Explanation:
1. Earth's curvature:
The primary reason for observing the roundness of the Earth from a high altitude is due to the curvature of the planet. As one ascends higher into the atmosphere, the horizon begins to curve away from the observer, creating the perception of a rounded Earth. This curvature is a result of the Earth's spherical shape.

2. Horizon:
From a height of six miles, the observer can see a noticeable curvature of the horizon. Instead of the horizon appearing as a straight line, it appears to be slightly curved. This curved horizon is a clear indication that the Earth is not flat.

3. Similar observations from space:
Astronauts who have traveled to space or observed the Earth from the International Space Station have consistently reported seeing a round Earth. The photographs and videos taken from space clearly show the spherical shape of our planet. These visual observations from space further support the conclusion that the Earth is round.

4. Scientific evidence:
In addition to visual observations, there is a wealth of scientific evidence supporting the round Earth theory. Measurements of the Earth's circumference, conducted through various methods such as triangulation and satellite technology, have provided accurate estimates of the planet's size and shape. These measurements confirm the roundness of the Earth.

Conclusion:
Observing the Earth from a height of six miles in the sky provides evidence of the Earth's roundness. The curved horizon and the consistent observations from space and scientific measurements all support the conclusion that the Earth is indeed round. This understanding of the Earth's shape has significant implications for various fields of science and our overall understanding of the world we live in.

Correct option is 'B', because in poem of geography lesson written by zulfikar ghose, first thing from the jet he notices that the earth is round.