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: Fission is a type of reproduction, but a baby is the result of sexual reproduction. 
Sentence2: the fallopian tubes are used to make babies.
[A]: baby


[Q]: Sentence1: Some mollusks are nearly microscopic. 
Sentence2: Some squids are nearly microscopic.
[A]: Some


[Q]: Sentence1: energy is used for heating a building by a heating system. 
Sentence2: buildings use a combination of production, exchange, and distribution of energy to regulate temperatures.
[A]:
building