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: plant requires seed dispersal for reproduction. 
Sentence2: plants are pollinated by birds.

Answer: plant


Question: Sentence1: Heterotrophs are living things that cannot make their own food. 
Sentence2: food contains organic molecules.

Answer: food


Question: Sentence1: Behaviors that improve fitness increase through natural selection. 
Sentence2: Adaptation traits contribute to individual fitness and to the evolution of animal genetic resources.

Answer:
fitness