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: if humans disturb animals in a location then those animals will move to a different location. 
Sentence2: The human being is self-aware.

A: humans
****
Q: Sentence1: threatening behavior by predators causes a porcupine to extend its quills. 
Sentence2: Fishers are predators that can eat porcupines.

A: predators
****
Q: Sentence1: All sound is created by vibrations. 
Sentence2: a rubber band snapping causes the particles to make sound.

A:
sound
****