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Our results support the hypothesis that the thermodynamically most favorable entry / exit portal for H2O is the so - called histidine gate ( HG ) , the same as for CO .
 Chemical: H2O; Chemical: histidine; Chemical: CO
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities: H2O, histidine, CO 
Answer:
 Chemical: H2O; Chemical: histidine; Chemical: CO