Answer:
If the earthworm's skin dries then they will not breath properly because moisture help them out to ease the diffusion of oxygen through its skin.
Explanation:
Hello,
Based on the required hypothesis, the best describing one considering the question "How is earthworm behavior affected by external stimuli?", would be:
If the earthworm's skin dries then they will not breath properly because moisture help them out to ease the diffusion of oxygen through its skin.
In this case, we are specifying a possible condition, this is "the earthworm's skin dries" which is a cause of an external stimuli (dryness). Next, we propose an effect, this is "they will not breath properly", that is caused by the initial part. Finally, we explain the effect via the cause "moisture help them out to ease the diffusion of oxygen through its skin" because is something testable via the subsequent experiments when considering the scientific method.
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