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.
One example is below.
Q: Sentence1: pesticides cause pollution. 
Sentence2: pollution can harm animals.
A: pollution.
Rationale: The word "pollution" is common to Sentence1 and Sentence2. So, it's a good answer.
Q: Sentence1: if soil is permeable then water easily flows through that soil. 
Sentence2: The increase in permeability is caused by the formation and expansion of ice in the soil.
A:
permeable