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: An example of a cartilaginous fish is a shark. 
Sentence2: jaws make sharks excellent predators.

Answer: shark


Question: Sentence1: With a spatula, fold in flour mixture. 
Sentence2: a sifter is used for separating flour.

Answer: flour


Question: Sentence1: Birds have relatively large brains and a high level of intelligence. 
Sentence2: Animals with feathers have brains.

Answer:
brains