21 IS ANSWER PLZ GIVE BRAINLYIST I NEED TO LEVEL UP
The correct answer is A.primary, because a primary landform is a natural feature on earth's surface.
It's called hypoxemia, it's low levels of oxygen in the blood, to be more specific, it's oxygen loss in your blood from your arteries. It can cause respiratory disorders, and tissue hypoxia, as a result of the blood not providing much oxygen to your body.
I hope I helped :)
