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: Carpools and vanpools can save time. 
Sentence2: vanpools decrease the amount of cars used to travel to a place.
[A]: vanpools


[Q]: Sentence1: Adaptation traits contribute to individual fitness and to the evolution of animal genetic resources. 
Sentence2: Behaviors can improve the evolution of animal genetic resources.
[A]: animal


[Q]: Sentence1: Allergies are an immune system response. 
Sentence2: Lymphocytes  are the key cells involved in allergies.
[A]:
Allergies