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: Algae have varied life cycles. 
Sentence2: And fish eat algae.

Answer: Algae


Question: Sentence1: Spikes are forceful the tidal waves of electric current. 
Sentence2: spikes come from tidal energy.

Answer: Spikes


Question: Sentence1: Birds move their wings using muscles in the chest. 
Sentence2: Bird flap their wings more quickly to fly faster.

Answer:
Birds