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.
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Question: Sentence1: Producers use energy and inorganic molecules to make food. 
Sentence2: Green plants use energy and inorganic molecules to make food.

Answer: energy


Question: Sentence1: Amphibians have permeable skin that easily absorbs substances from the environment. 
Sentence2: Some substances are harmful to the body and block biological systems.

Answer: substances


Question: Sentence1: cooking food requires adding heat energy. 
Sentence2: humans add heat energy to their food.

Answer:
energy