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: Mad Cow disease is a concern. 
Sentence2: pathogens can cause Mad Cow.

A: Cow
****
Q: Sentence1: Leaves make food for the plant. 
Sentence2: Some producers have leaves to help use energy and inorganic molecules.

A: Leaves
****
Q: Sentence1: Some viruses can cause cancer. 
Sentence2: Cancer requires an accumulation of mutations.

A:
cancer
****