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: Generally, pheromones are volatile substances. 
Sentence2: Male dogs use volatile substances in urine to mark their territory.
[EX A]: substances

[EX Q]: Sentence1: Nitrogen is found in proteins, nucleic acids, and chlorophyll. 
Sentence2: Life without protein is impossible.
[EX A]: proteins

[EX Q]: Sentence1: erosion causes deposition. 
Sentence2: Erosion contributes to forming stalactites and stalagmites.
[EX A]:
erosion