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: a flashlight requires a source of electricity to produce light. 
Sentence2: Flashlights provide the safest emergency lighting source.
[EX A]: flashlight

[EX Q]: Sentence1: Lymphocytes are the key cells involved in the immune response. 
Sentence2: The key cells involved in the immune response produce antibodies.
[EX A]: cells

[EX Q]: Sentence1: Annelids are worms such as the familiar earthworm. 
Sentence2: Moles eat some Annelids.
[EX A]:
Annelids