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: folding an object causes that object to change shape. 
Sentence2: Folding an object causes that object to transform.

SOLUTION: causes

PROBLEM: Sentence1: a fire requires oxygen to burn. 
Sentence2: Oxygen has  eight protons and eight electrons.

SOLUTION: oxygen

PROBLEM: Sentence1: Aging occurs as cells lose their ability to divide. 
Sentence2: Aging occurs because there are less cells produced.

SOLUTION:
Aging