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: Tree-ring dating the 1700 Cascadia earthquake. 
Sentence2: estimating the age of trees can be used in reviewing earthquake history.
earthquake

Sentence1: plant requires seed dispersal for reproduction. 
Sentence2: plants are pollinated by birds.
plant

Sentence1: Antibiotics have no effect on viruses. 
Sentence2: Infection with Cyclospora is treatable with antibiotics.

Antibiotics