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: Acid rain is precipitation which pH is 5.7 or lower. 
Sentence2: gases from burning coal causes precipitation which pH is 5.7 or lower.
[A]: 5


[Q]: Sentence1: Among monogamous species of birds and mammals, both parents often care for their offspring. 
Sentence2: The period of parental care after birth for manogamous species are handled by both parents.
[A]: monogamous


[Q]: Sentence1: Furthermore, such laser light is polarized. 
Sentence2: lasers are polarized.
[A]:
polarized