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: Chordates have a complete digestive system and a closed circulatory system. 
Sentence2: All chordates are vertebrates.
[A]: Chordates


[Q]: Sentence1: creating wood-free paper does not require cutting down trees. 
Sentence2: creating printed media requires cutting down trees.
[A]: creating


[Q]: Sentence1: Electron microscope is developed in Germany. 
Sentence2: viruses are so small that they can be seen only with a device developed in germany.
[A]:
Germany