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: bacteria can cause people to become ill. 
Sentence2: bacteria can cause people to die.

SOLUTION: bacteria

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

SOLUTION: digestion

PROBLEM: Sentence1: Most hormones are regulated by feedback mechanisms. 
Sentence2: enzymes control hormones.

SOLUTION:
hormones