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.

[EX Q]: Sentence1: sharpening an object causes that object to change shape. 
Sentence2: sharpening a knife causes it to change shape.
[EX A]: causes

[EX Q]: Sentence1: Hydrogen bonds cause water to expand when it freezes. 
Sentence2: Hydrogen bonds Hydrogen bonds are primarily electrostatic in origin.
[EX A]: Hydrogen

[EX Q]: Sentence1: Reptile parents provide little if any care to their young. 
Sentence2: Crocodilian mothers are the most attentive reptile parents.
[EX A]:
Reptile