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Upon the initial introduction of the DMMP solution to a previously H ( 2 ) O - saturated surface , DMMP diffuses into the porous layer and displaces weakly hydrogen - bonded H ( 2 ) O molecules .
 DMMP, H ( 2 ) O, DMMP, hydrogen, H ( 2 ) O
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 DMMP, H ( 2 ) O, DMMP, hydrogen, H ( 2 ) O