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: All oaks are trees. 
Sentence2: Cutting down oaks has a negative impact on an ecosystem.
answer:
oaks


question:
Sentence1: Protozoa make humans sick when they become human parasites. 
Sentence2: paramecium are single celled animals that make humans sick when they become human parasites.
answer:
become


question:
Sentence1: Lymphocytes are the key cells involved in the immune response. 
Sentence2: B lymphocytes produce antibodies .
answer:

Lymphocytes