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


[Q]: Sentence1: Asbestos is a dangerous carcinogen. 
Sentence2: Asbestos causes cancer.
[A]: Asbestos


[Q]: Sentence1: If fertilized, the egg implants itself in the uterus. 
Sentence2: the egg implants itself in the uterus after sperm swim to an egg.
[A]:
egg