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.

Q: Sentence1: Propane can be either a liquid or a gas. 
Sentence2: heat can be added to propane to change it's properties through the boiling process.

A: Propane
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Q: Sentence1: forming coal requires decaying vegetation. 
Sentence2: Forming fossil fuels requires decaying vegetation.

A: decaying
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Q: Sentence1: Some species of reptiles can go several weeks between meals. 
Sentence2: Some species of reptiles can go several weeks between time when bile is diverted into the gallbladder.

A:
Some
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