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: Fertilization occurs naturally in the fallopian tubes. 
Sentence2: fertilization is used for reproduction.
[EX A]: Fertilization

[EX Q]: Sentence1: Heterotrophs get food by eating other living things. 
Sentence2: fish eat other living things.
[EX A]: living

[EX Q]: Sentence1: a doorbell converts electrical energy into sound. 
Sentence2: a doorbell converts electrical energy into what we hear.
[EX A]:
converts