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.

Sentence1: Acids dissolve in base and turn blue litmus red. 
Sentence2: acid changes color.
Acids

Sentence1: Batteries are a better source of DC electricity. 
Sentence2: a flashlight requires batteries to produce light.
Batteries

Sentence1: Protists Protists are single-celled organisms. 
Sentence2: Most single-celled organisms have motility.

organisms