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: an image in a mirror is formed by reflecting light. 
Sentence2: mirrors can be seen with our eyes.
answer:
mirror


question:
Sentence1: Cells are the microscopic building blocks of organisms. 
Sentence2: proteins are the building blocks of organisms.
answer:
organisms


question:
Sentence1: Oncogenes promote the division of cells with damaged DNA. 
Sentence2: cancer promotes the division of cells with damaged DNA.
answer:

DNA