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: Mitosis is cell division. 
Sentence2: mitosis often causes growth.
[EX A]: Mitosis

[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: if remains of prehistoric life are found in a place then that place used to be covered by water.
[EX A]: be

[EX Q]: Sentence1: Starfish and sea urchins are also echinoderms. 
Sentence2: Sea urchins lack a centralized nervous system.
[EX A]:
sea