Which of the following is a unique feature of the Earth's environment that aerospace engineers needed to imitate on a spacecraft in order to make manned spaceflight possible?

A. The Earth has a strong magnetic field.
B. The Earth has an atmosphere rich in carbon dioxide and hydrogen.
C. The Earth has a strong gravitational field.
D. The Earth has an atmosphere rich in nitrogen and oxygen.

The answer is B

Explanation:

The Earth has an atmosphere rich in nitrogen (78%) and oxygen (20%). Aerospace engineers have designed systems that supply astronauts with air that is very similar in composition to Earth's atmosphere. This means that the air fed into spacecraft is mostly nitrogen and oxygen.

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hi there!

out of the two, (b) precision would be more reasonable.   however, both a and b could be pretty reasonable.

-awesomerepublic   : )