# Quiz

+ What are the following statements incorrect?
  + `A` . The essence of. label is a scheduling system that can artificially control where region replica are stored 
  + `B` . Label needs to be configured on PD and TiKV
  + `C` . Isolation-level corresponds to the data center (DC) for maximum availability
  + `D` . If all replica of a region are not available, it is possible that the entire TiDB database will be unavailable

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C