The phrases above are describing what layer of our atmosphere?
A) actinosphere
B) exosphere
C) ionosphere
D) thermosphere

Fades into outer space

No clear upper boundary  

Not all scientists agree that it is part of atmosphere

The phrases above are describing B) exosphere layer of our atmosphere

Explanation:

The exosphere is the uppermost region of Earth's atmosphere as it gradually fades into the vacuum of space. Air in the exosphere is extremely thin - in many ways it is almost the same as the airless void of outer space.The exosphere is perfect for placing satellites as there is very little friction and they are able to orbit fairly easily without being disrupted. Most of the molecules that exist in the exosphere end up being pulled back into earth's lower atmospheric levels by gravity.The air in the exosphere is very thin, and is made up mostly of helium, and hydrogen. Traces of other gases such as atomic oxygen and carbon dioxide can also be found. The upper level of the exosphere is the farthest point from earth that is still affected by earth's gravity.The exosphere is an important atmospheric layer as it functions as a transition zone between the earth's atmosphere and outer space It is the layer in which we can find artificial satellites that carry out constant studies of the earth and outer space. It also acts as a transit zone towards outer space.