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: looking at bright objects has a negative impact on the eyes. 
Sentence2: Looking at bright objects have a negative impact on the retina.
[A]: bright


[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: Water density decreases with temperature and increases with salt content. 
Sentence2: Salt content increases melting points of solids.
[A]:
content