Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.
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Question: Sentence1: threatening behavior by predators causes a porcupine to extend its quills. 
Sentence2: Fishers are predators that can eat porcupines.

Answer: predators


Question: Sentence1: Rainy clouds cause rain, and excess water vapor from clouds is the basis of rainbows. 
Sentence2: Condensation can lead to rain.

Answer: rain


Question: Sentence1: Milk is a nutritious fluid. 
Sentence2: milkshakes are a nutritious fluid.

Answer:
fluid