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: if fossils of a water animal or plant are found in a place then that place used to be covered by water in the past. 
Sentence2: Fossils are the remains of prehistoric life.
[EX A]: fossils

[EX Q]: Sentence1: Interest in fossils is worldwide. 
Sentence2: paleontologists study something with worldwide interest.
[EX A]: Interest

[EX Q]: Sentence1: Echinoderms have a unique water vascular system with tube feet. 
Sentence2: deuterostomes can have a water vascular system with tube feet.
[EX A]:
feet