When we breathe, our respiratory system takes up oxygen and carbon dioxide or other useless gases go out . The oxygen combines with the haemoglobin in the blood of the circulatory system . This is transferred to all the cells of our body to get energy.
Answer : Hydrogen.......:
I believe they cannot start with big trees and bushes because the there is not enough nutrients in the soil, so instead pioneer species pave the way for primary succession.
Venus is the answer, you can tell easily because Venus has no moons or rings :)
False because the third line of defense is specific by identifying the foreign antigen and activating the antibodies that can bind to the invaders and eliminating the spread
