# Quiz

+ What is incorrect about the Percolator transaction execution process?
  + `A` . Client is the coordinator of the two-phase submission
  + `B` . Each transaction has a start_ts timestamp that records the start time of the transaction
  + `C` . Prewrite operations cannot be rolled back
  + `D` . If the primary key is already committed, it will not affect atomicity even if it fails

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C
2. What is incorrect about the Percolator transaction execution process?
 Client is the coordinator of the two-phase submission
 Each transaction has a start_ts timestamp, which is used to record the transaction start time
 Prewrite operations cannot be rolled back
 If the primary key has already been committed, atomicity will not be affected even if a failure occurs