The answer is C
Completing multiple trials during an experiment
The rest of the options are possibilities of how you can "mess up" and experiment, but if you run multiple trials doing everything right, for example, making sure all variables are controlled, using the right equipment, and making sure you cover all possible variables. If you make sure you do multiple trials and you do them right, you get successful results.
So the answer is C
I hope this was helpful :)
Goodluck!!
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Answer:
I think I it is selective breeding also known as artificial selection
<span>Each of the protein chains are conjugated to a nonprotein heme group.Hemoglobin is
the protein that's made of the four polypeptide chains. Each of these chains contains a heme group. Red blood cells are primary players in the oxygen hauling, and they wouldn't be able to do their job if it the weren't for a special molecule called the heme.</span>
The answer is C. The brain stem controls blood circulation.