Why is blood obtained through veins and not from arteries when collecting blood?

When fossil fuels are burned, carbon dioxide is released. how does this gas impact the environment?

Although cellular respiration involves many steps, the whole process can be represented by a single equation. a + b → c + d + e which substances would complete the equation that models the overall process of cellular respiration? a: b: c: d: e:

What dose the oxygen produce in photosynthesis comes from