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: gills are used for breathing water by aquatic animals. 
Sentence2: gills are used for breathing water by sharks.
answer:
are


question:
Sentence1: Enveloped viruses make their own membranes. 
Sentence2: Some viruses make their own membranes.
answer:
make


question:
Sentence1: Breathing gets oxygen into the body, but aerobic respiration occurs at the cellular level. 
Sentence2: That the cellular level, the final stage of breathing oxygen is electron transport.
answer:

Breathing