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: the ovaries are used in reproduction. 
Sentence2: Unlike most female animals, which have two functioning ovaries, the chicken usually has only one.

A: ovaries
****
Q: Sentence1: For example, insulin is a protein hormone. 
Sentence2: Insulin is produced in a part of the cell called the ribosome.

A: insulin
****
Q: Sentence1: Increased atmospheric carbon dioxide increases greenhouse effect and warms the earth. 
Sentence2: burning fossil fuels warms the earth.

A:
earth
****