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: cold fronts cause thunderstorms as they pass by. 
Sentence2: Cold fronts cause lightning.
[EX A]: cold

[EX Q]: Sentence1: Mollusks are invertebrates such as the common snail. 
Sentence2: Another common snail is the decollate snail.
[EX A]: snail

[EX Q]: Sentence1: Animals and humans eat plants for their nutrients. 
Sentence2: changes in soil pH rob humans of nutrients.
[EX A]:
humans