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.

Sentence1: Eggs are usually laid in a nest. 
Sentence2: birds have nests.
nest

Sentence1: Insects spread disease and destroy crops. 
Sentence2: Crops are plants that are grown for food or other uses.
crops

Sentence1: the emission of sulfur dioxide causes acid rain. 
Sentence2: Scrubbers significantly reduce emissions of sulfur dioxide.

dioxide