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: Plants exhibit phototropism, or growing toward a light source. 
Sentence2: Bamboos are vigorous, rugged plants.
[EX A]: Plants

[EX Q]: Sentence1: Mollusks are invertebrates such as the common snail. 
Sentence2: snails have no backbone.
[EX A]: snail

[EX Q]: Sentence1: Life without protein is impossible. 
Sentence2: life without nitrogen is impossible.
[EX A]:
Life