TASK DEFINITION: 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.
PROBLEM: Sentence1: Mammalian teeth are important for digestion. 
Sentence2: bats' teeth are important for digestion.

SOLUTION: digestion

PROBLEM: Sentence1: Humans have collected and grown mushrooms for food for thousands of years. 
Sentence2: humans have collected and grown porcinis for thousands of years.

SOLUTION: Humans

PROBLEM: Sentence1: Kidney failure may be treated with dialysis. 
Sentence2: Kidney failure may be treated by the mechanical process of cleaning the blood.

SOLUTION:
Kidney