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: ultraviolet light causes sunburn. 
Sentence2: Sunburn risk is higher at elevation.
answer:
sunburn


question:
Sentence1: All life relies on a relatively narrow range of pH, or acidity. 
Sentence2: humans rely on a relatively narrow range of acidity.
answer:
acidity


question:
Sentence1: Mollusks in the diorama include snails and clams. 
Sentence2: clams are mollusks.
answer:

clams