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: Ferns are vascular plants. 
Sentence2: when a fern grows, its size of leaves may increase.

Answer: Ferns


Question: Sentence1: Organisms cluster around hydrothermal vents in the ocean floor. 
Sentence2: vents on the ocean floor are powered by heat.

Answer: vents


Question: Sentence1: Some species of reptiles can go several weeks between meals. 
Sentence2: Some species with scales or plates can go several weeks between meals.

Answer:
Some