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: Muscles can only contract. 
Sentence2: Contraction is a type of movement.

A: contract
****
Q: Sentence1: sonar is used to find the location of an object. 
Sentence2: Surface ships use sonar to locate and track submarines.

A: location
****
Q: Sentence1: oil is formed by layers of sediment pushing down on decomposing algae. 
Sentence2: Fossil fuels like coal and oil are ancient biomass fuel.

A:
oil
****