CROSSING OVER
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The correct answer is A.primary, because a primary landform is a natural feature on earth's surface.
Answer:
Oxygen or Minerals or Sugars (Oxygen is the most relevant one)
Explanation:
To survive, every cell must have a constant supply of vital substances such as sugar, minerals, and oxygen, and dispose of waste products, all carried back and forth by the blood cells. Without these substances, cells would die in a very short period of time.
