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: Limestone caves displaying stalactites. 
Sentence2: Limestone caves are formed by depositions.

Answer: Limestone


Question: Sentence1: a mutation in the sex cells of a parent can cause a new trait to appear in the parent 's offspring. 
Sentence2: cancer of a parent's cells can cause a new trait to appear in their offspring.

Answer: appear


Question: Sentence1: Bird beaks are generally adapted for the food they eat. 
Sentence2: Bird beaks are often adapted for eating fish.

Answer:
Bird