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: air pollution can cause the pH of soil to decrease. 
Sentence2: Acidity is measured with a pH meter or with pH paper strips.
[A]: pH


[Q]: Sentence1: Excretion is the process of removing wastes and excess water from the body. 
Sentence2: parasites remove waste from their bodies.
[A]: wastes


[Q]: Sentence1: the Earth being tilted on its rotating axis causes seasons. 
Sentence2: the Earth being tilted on its rotating axis causes winter.
[A]:
Earth