9991
2. Our study involved a group of 60 male and female subjects who were exposed to MTBE and benzene -contaminated water concentrations up to 76 PPB for MTBE and 14 PPB for benzene , for a period of 5 to 8 years.
 None
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: RNA,cell type,protein,cell line,DNA, Arguments type: . 
Text: {0} 
Answer:
 None