10669
Since Cu is a redox active transition metal , we hypothesized that oxidative stress would be the main mechanism underlying cell toxicity .
 Chemical: Cu; Chemical: transition metal
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: Cu, transition metal 
Answer:
 Chemical: Cu; Chemical: transition metal