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: harming an animal species causes that animal 's population to decrease. 
Sentence2: Wild animal populations have decreased drastically, due to both hunting and loss of habitat.

SOLUTION: animal

PROBLEM: Sentence1: Hydrogen bonds cause water to expand when it freezes. 
Sentence2: Hydrogen bonds Hydrogen bonds are primarily electrostatic in origin.

SOLUTION: Hydrogen

PROBLEM: Sentence1: when an electrical circuit is working properly , electrical current runs through that circuit. 
Sentence2: When a circuit is working properly, a charge in motion runs through that circuit.

SOLUTION:
circuit