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: riding a bike does not cause pollution. 
Sentence2: riding a bike does not release particles.
[A]: bike


[Q]: Sentence1: Passive immunity lasts only as long as the antibodies survive in body fluids. 
Sentence2: A pregnant woman will pass antibodies to the fetus.
[A]: antibodies


[Q]: Sentence1: Some receptors are free nerve endings. 
Sentence2: free nerve endings can be found in the skin.
[A]:
endings