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: An organism can gain energy by assimilation or absorption of food. 
Sentence2: Organisms require food for growth.
[EX A]: food

[EX Q]: Sentence1: Soil Erosion Soil erosion is a natural process. 
Sentence2: wind and rain is a natural process.
[EX A]: natural

[EX Q]: Sentence1: Mammals that are viviparous are called therian mammals. 
Sentence2: By Jurassic times, mouse-sized therians with jaws and hair had evolved.
[EX A]:
therian