instruction:
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.
question:
Sentence1: nectar is used for attracting pollinators by plants. 
Sentence2: butterflies pollinate plants.
answer:
plants


question:
Sentence1: camouflage is used for protection by prey against predators. 
Sentence2: blending is used for protection.
answer:
protection


question:
Sentence1: Bird eggs have hard, calcium carbonate shells. 
Sentence2: The reproductive cells of a bird is a hard, calcium carbonate shell.
answer:

calcium