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.

[EX Q]: Sentence1: Fertilization is the penetration of the egg by a sperm. 
Sentence2: Sperm must swim from the male to the female egg.
[EX A]: egg

[EX Q]: Sentence1: Batteries are a better source of DC electricity. 
Sentence2: a flashlight requires batteries to produce light.
[EX A]: Batteries

[EX Q]: Sentence1: natural magnetism is used for pointing north by a compass. 
Sentence2: poles are used to point with a compass.
[EX A]:
compass