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: Fully cooking oysters kills the bacteria. 
Sentence2: Fully cooking oysters can prevent illness.

A: Fully
****
Q: Sentence1: smell is used for finding food by some animals. 
Sentence2: Food includes small rodents and birds.

A: food
****
Q: Sentence1: When carbon dioxide is in water, it creates carbonic acid. 
Sentence2: a cavern is formed by carbon dioxide is in groundwater seeping through rock and dissolving limestone.

A:
carbon
****