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: Lymphocytes are the key cells involved in the immune response. 
Sentence2: The key cells involved in the immune response produce antibodies.

A: cells
****
Q: Sentence1: Cells are the microscopic building blocks of organisms. 
Sentence2: proteins are the building blocks of organisms.

A: organisms
****
Q: Sentence1: Sight is the ability to sense light, and the eye is the organ that senses light. 
Sentence2: Sight is the process of organized images falling on the retina.

A:
Sight
****