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: Mammals generate heat mainly by keeping their metabolic rate high. 
Sentence2: food keeps mammals' metabolic rates high.
Mammals

Sentence1: a plant requires sunlight to grow. 
Sentence2: Grass needs air and sunlight.
sunlight

Sentence1: electrical current running through a wire causes that wire to heat up. 
Sentence2: High currents allow too much power, or electrical energy to be wasted in wires in the form of heat.

electrical