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: All sharks are predators. 
Sentence2: hiding can be used for avoiding sharks.
[A]: sharks


[Q]: Sentence1: triceps contracting causes a person 's elbow to straighten. 
Sentence2: muscles contracting cause a person's elbow to straighten.
[A]: contracting


[Q]: Sentence1: Ancestors of hagfish are thought to have been the earliest vertebrates. 
Sentence2: Property of ancestors and forefathers can only be legally inherited by sons.
[A]:
Ancestors