23843
Out of 35 antibiotic - essential oil pairs tested , four of them showed synergistic effect ( FIC <= 0 . 5 ) and 31 pairs showed no interaction ( FIC > 0 . 5 - 4 . 0 ) .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None