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: Humans have collected and grown mushrooms for food for thousands of years. 
Sentence2: Yeast and mushrooms are types of fungus.
[A]: mushrooms


[Q]: Sentence1: evaporation can be used for separating a solute from a solvent in a solution. 
Sentence2: Evaporation can be used for segregation a solute from a solvent in a solution.
[A]: a


[Q]: Sentence1: Trees produce oxygen. 
Sentence2: Oxygen has a positive impact on an ecosystem.
[A]:
oxygen