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: Carbon dioxide is controlled by the carbon cycle. 
Sentence2: Carbon dioxide is controled by the carbon circle and is transferred between organisms and atmosphere.
[A]: controlled


[Q]: Sentence1: Most water comes from precipitation. 
Sentence2: aquatic animals require precipitation to survive.
[A]: precipitation


[Q]: Sentence1: a wildfire changes an ecosystem drastically. 
Sentence2: Very large ecosystems are known as biomes .
[A]:
ecosystem