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: Mad Cow disease is a concern. 
Sentence2: pathogens can cause Mad Cow.

Answer: Cow


Question: Sentence1: creating paper requires cutting down trees. 
Sentence2: Trees begin as epiphytes on host trees.

Answer: trees


Question: Sentence1: Good visibility is essential for safe driving. 
Sentence2: bad weather impairs safe driving.

Answer:
driving