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: Protozoa make humans sick when they become human parasites. 
Sentence2: paramecium are single celled animals that make humans sick when they become human parasites.

Answer: become


Question: Sentence1: Spikes are forceful the tidal waves of electric current. 
Sentence2: spikes come from tidal energy.

Answer: Spikes


Question: Sentence1: vein deposits of gold and silver are formed by igneous intrusion. 
Sentence2: vein deposits of precious metals are formed by igneous intrusion.

Answer:
deposits