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: an animal requires air for survival.
Sentence2: The Moon has no atmosphere and no air.
[A]: air

[Q]: Sentence1: Oxygen fatigue is a shortage of oxygen reaching the brain.
Sentence2: Plants can reduce fatigue during the daytime.
[A]: fatigue

[Q]: Sentence1: Sporangia produce spores that develop into tiny, heart-shaped gametophytes.
Sentence2: Gametophytes of extant genera are green, photosynthetic,and have a long ribbon shaped thallus.
[A]:
heart-shaped