Answer:
They are veins and arteries. The primary function of arteries is to transport highly oxygenated, nutrient-rich blood from our hearts and distribute it to the rest of our body. Veins, on the other hand, are used to pump much-needed blood back to the heart.
Explanation:
The sun heats the earth through radiation. Since there is no medium (like the gas in our atmosphere) in space, radiation is the primary way that heat travels in space. When the heat reaches the earth it warms the molecules of the atmosphere, and they warm other molecules and so on.
