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: Energy enters ecosystems in the form of sunlight or chemical compounds. 
Sentence2: Energy enters ecosystems in the form of photons.

Answer: Energy


Question: Sentence1: Bees feed on nectar and pollen. 
Sentence2: Plant reproduction often requires bees and nectar.

Answer: Bees


Question: Sentence1: Human Embryonic Development Follows human development from fertilization through birth. 
Sentence2: Pregnancy is  embryonic development.

Answer:
Development