20. His parents were teachers in that school, _______ lost their lives in order to save

their students in the earthquake. 

A．none of them

B．both of them

C．none of whom

D．both of whom

《湖北省农村信用社安全保卫工作制度》（鄂农信发[2013]23号）规定，防尾随联动门使用指纹门禁系统，非营业室内勤人员不得设置指纹权限，人员调离及时销户。