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In the study , a rat myocardial cell line ( H9c2 ) exposed to different concentrations of nickel chloride ( NiCl ( 2 ) ) displayed apoptotic features accompanied by reactive oxygen species generation .
 Chemical: nickel chloride; Chemical: NiCl ( 2 ); Chemical: oxygen
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: nickel chloride, NiCl ( 2 ), oxygen 
Answer:
 Chemical: nickel chloride; Chemical: NiCl ( 2 ); Chemical: oxygen