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: Habitat destruction is the primary cause of extinction or threat of extinction for all animals. 
Sentence2: building housing developments may cause extinction.
[A]: extinction


[Q]: Sentence1: if an object is kicked then force is exerted on that object. 
Sentence2: if an object is kicked then a measurement of newtons is exerted on that object.
[A]: exerted


[Q]: Sentence1: Refrigerate cold foods at 40 degrees F or lower until serving time. 
Sentence2: Keeping food at 40 degrees F or lower is used for keeping food fresh.
[A]:
40