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: Dinosaur bones, like many other artifacts, are fossilized. 
Sentence2: radioactive dating is used to determine the age of dinosaur bones.
[A]: Dinosaur


[Q]: Sentence1: the emission of sulfur dioxide causes acid rain. 
Sentence2: Sulfur dioxide emissions causes soil nutrients to be leached away.
[A]: dioxide


[Q]: Sentence1: Birds are endothermic tetrapod vertebrates. 
Sentence2: Animals in the class aves are endothermic tetrapod vertebrates.
[A]:
are