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


[Q]: Sentence1: an animal usually requires a warm body temperature for survival. 
Sentence2: Warm blooded animals have a constant body temperature.
[A]: animal


[Q]: Sentence1: Transcription takes place in the nucleus. 
Sentence2: All cells have a nucleus.
[A]:
nucleus