instruction:
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.
question:
Sentence1: Cells are the units of function in living things. 
Sentence2: living things cannot survive without oxygen.
answer:
living


question:
Sentence1: Oxygen fatigue is a shortage of oxygen reaching the brain. 
Sentence2: Plants can reduce fatigue during the daytime.
answer:
fatigue


question:
Sentence1: bacteria cause food to spoil. 
Sentence2: milk can be made undrinkable by bacteria.
answer:

bacteria