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.

when jerome paddle in flowing river towards east the net speed of jerome will increase

so the net speed of jerome will be given as

now the speed of paul will be same as it is given as he is running on the ground

so

so here we can say since the speed of jerome is more so he will win the race

now as we know the distance so the time difference is given as

so jerome will reach first and the time difference will be 203.55 s or 3.4 min

the journeys of marquette, joliet and la salle a) new france expand.

all three of these explorers explored the midwest and the area around the great lakes, which they subsequently claimed for france.

this was a big portion of territory and expanded new france which before then only consisted of quebec province in northeastern canada