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: Fertilization is the penetration of the egg by a sperm. 
Sentence2: Sperm must swim from the male to the female egg.
answer:
egg


question:
Sentence1: forming coal requires decaying vegetation. 
Sentence2: Forming fossil fuels requires decaying vegetation.
answer:
decaying


question:
Sentence1: a pulley is used for lifting objects. 
Sentence2: Tower cranes use pulleys to lift loads.
answer:

lifting