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.

[Q]: Sentence1: Amphibians have permeable skin that easily absorbs substances from the environment. 
Sentence2: permeable skin easily absorbs air to breathe through.
[A]: absorbs


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


[Q]: Sentence1: Head hair is especially important in preventing heat loss from the body. 
Sentence2: Head hair is especially important in preventing hypothermia.
[A]:
Head