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: Mollusks are invertebrates such as the common snail. 
Sentence2: Another common snail is the decollate snail.
[A]: snail


[Q]: Sentence1: Fertilization occurs naturally in the fallopian tubes. 
Sentence2: fertilization is used for reproduction.
[A]: Fertilization


[Q]: Sentence1: operating an automobile usually requires fossil fuels. 
Sentence2: Dinosaur bones and petrified wood are examples of fossil fuels.
[A]:
fossil