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: threatening behavior by predators causes a porcupine to extend its quills. 
Sentence2: Fishers are one of the few specialized predators on porcupines.

A: predators
****
Q: Sentence1: if an object is made of a material then that object has the properties of that material. 
Sentence2: If an object is made of a drug, then that object has the properties of that drug.

A: made
****
Q: Sentence1: Tobacco smoke consists of solid particles and gases. 
Sentence2: Lung cancer is most often caused by exposure to solid particles and gases.

A:
gases
****