A student conducts an experiment to test the hypothesis that caffeine increases the heart rate of daphnia (water fleas). She places a daphnia on a microscope slide in a drop of water and measures its heart rate. She then adds a drop of caffeine solution and measures the heart rate again. To ensure the reliability of her results, which of the following is the most important next step?
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A
Testing a different type of organism to see if it reacts the same way.
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B
Using a stronger concentration of caffeine to get a more obvious result.
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C
Repeating the experiment multiple times with different daphnia.
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D
Publishing her single result immediately to claim the discovery.