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: All sharks are predators. 
Sentence2: hiding can be used for avoiding sharks.
sharks

Sentence1: if fossils of a water animal or plant are found in a place then that place used to be covered by water in the past. 
Sentence2: Common fossils include plant fossils like ferns.
plant

Sentence1: Ethologists are scientists who study animals in their natural habitats. 
Sentence2: scientists study animals behavior.

scientists