It seems that you have missed the necessary options for us to answer this question so I had to look for it. Anyway, here is the answer. Varicose veins seen in the superficial veins of the legs are unsightly and often treated by surgically removing them. however, even without these veins being present, the return of all blood toward the heart from the legs is not diminished primarily because <span>blood can still return via the deep veins. Hope this helps.</span>
I believe it’s Cellular Respiration.
Create a mindset that blocks you from accepting that certain things in life are true.
Gases in Earth's Atmosphere. Nitrogen and Oxygen are by far the most common. Dry air is composed of about 78% Nitrogen (N2) and about 21% Oxygen (O2). Argon, Carbon Dioxide (CO2), and many other gases are also present in much lower amounts; each makes up less than 1% of the atmosphere's mixture of gases.
So therefore Oxygen is the gas that makes up the largest portion of the Earths Atmosphere.
