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: 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: Mitosis is cell division. 
Sentence2: mitosis often causes growth.
answer:
Mitosis


question:
Sentence1: Skin color is determined by the melanin pigment in the skin cells. 
Sentence2: Melanin pigment is determined by a polygenic trait.
answer:

melanin