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: a fire requires oxygen to burn. 
Sentence2: Oxygen has  eight protons and eight electrons.

Answer: oxygen


Question: Sentence1: Genetics is the study of inheritance. 
Sentence2: Pedigrees are useful tools for studying genetics.

Answer: Genetics


Question: Sentence1: Speeding can be dangerous and increase stress. 
Sentence2: Force can cause objects to speed up, which is dangerous.

Answer:
dangerous