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.

[EX 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.
[EX A]: controlled

[EX Q]: Sentence1: burning fossil fuels increases the carbon in the atmosphere. 
Sentence2: the byproduct of fossil fuels is carbon.
[EX A]: carbon

[EX Q]: Sentence1: HIV, the human immunodeficiency virus, is a retrovirus. 
Sentence2: The human immunodeficiency virus infects and detroys helper T cells.
[EX A]:
human