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: All chemical reactions require activation energy to get started. 
Sentence2: Catalysts lower the activation energy.

SOLUTION: activation

PROBLEM: Sentence1: Light is the visible form of electromagnetic energy. 
Sentence2: Electromagnetic energy enters the eye through an opening called the pupil.

SOLUTION: electromagnetic

PROBLEM: Sentence1: carbon dioxide concentrations in the air have increased over the last decade dramatically. 
Sentence2: Increases in carbon dioxide make the greenhouse effect worse.

SOLUTION:
carbon