The respiratory system always needs iron. The red blood cells are in charge of the transport of O2. They need iron to do this.
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There is no image or choices so what exactly do you want us to answer.
Answer:
A. Specialized cells are made up of tissues
Explanation:
Cells make up tissues, tissues make up organs, organs make up organ systems and organ systems make up an organism.
All the other options are correct, but cells are not made up of tissues.
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)Sexual reproduction maintains a constant level of variation in the population and requires less energy.
The genotypic ratio of their offspring is 100% Ee.
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-vf
