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


[Q]: Sentence1: Limestone caves displaying stalactites. 
Sentence2: Limestone caves are formed by depositions.
[A]: Limestone


[Q]: Sentence1: Plants are multicellular eukaryotes with cell walls made of cellulose. 
Sentence2: Plants have nuclei.
[A]:
Plants