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.

Sentence1: hunting requires seeing prey. 
Sentence2: hunting requires seeing an animal.
hunting

Sentence1: Passive immunity lasts only as long as the antibodies survive in body fluids. 
Sentence2: A pregnant woman will pass antibodies to the fetus.
antibodies

Sentence1: gases from burning coal and oil dissolving in water in the atmosphere causes acid rain. 
Sentence2: Coal-fired plants Are power stations which burn coal to generate electricity.

burning