I believe the answer is oxygen only
Answer:
Pioneer species is the general name for the first organisms to move into a disturbed environment or to grow after a volcanic eruption covers an area with lava.
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includes the brain and spinal cord
The correct answer is: a tourniquet.
The tourniquets are tight straps around an arm or leg and tightened to stop bleeding, used to control arterial and venous blood flow. In the past, tourniquet are used to control bleeding during amputations. Now, a tourniquet is used in surgeries to block arterial blood flow following and to minimize blood loss.
