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: Hair helps to insulate and protect the body. 
Sentence2: most mammals have insulation that also protects the body.
body

Sentence1: an automobile engine transforms chemical energy into mechanical energy. 
Sentence2: cars transform chemical energy into mechanical energy.
chemical

Sentence1: Plants use sunlight to make energy. 
Sentence2: Most ecosystems get energy from plants.

Plants