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: when a gas in an open container evaporates , that gas spreads out into the air. 
Sentence2: If you place gas in an open box it will evaporate and spread out into the air.

Answer: gas


Question: Sentence1: Trees have woody stems covered with bark. 
Sentence2: Evergreens have woody stems covered with bark.

Answer: bark


Question: Sentence1: natural disasters can cause animals to leave an environment. 
Sentence2: natural disasters can cause goats to leave an environment.

Answer:
disasters