The medication would be the controlled variable, the factor that remains constant.
Explanation:
Genes are located on chromosomes, which are large pieces of DNA contained in a eukaryotic cell's nucleus.
They produce narrow-band high-frequency sound to help them navigate in water. These high-frequency sounds are used in echolocation. Echolocation is used to identify and locate prey and also avoid the predators. Marine mammals like whales and dolphin use echolocation in different manners.
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