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: Mollusks are invertebrates such as the common snail. 
Sentence2: snails have no backbone.
[A]: snail


[Q]: Sentence1: Interstellar space contains a plasma. 
Sentence2: interstellar space contains electrons, atoms, and stars.
[A]: Interstellar


[Q]: Sentence1: when an animal moves , chemical energy is converted to mechanical energy. 
Sentence2: Animals are inefficient energy converters.
[A]:
converted