You are working on a database， where you have three redo log groups. When the database is down for a backup， an operating system （OS） user deletes all the redo log files in a group. What will happen when you open your database？（）

A. The instance starts， the database is mounted， but efforts to open the database fail， and an error about the missing redo log group is displayed.

B. Before the instance starts， you receive an error about the missing redo log files of a group.

C. The instance starts and the database opens with an error message written to the alert log file.

D. The instance starts and the database opens because two redo log groups still exist.

E. The instance starts and the database opens， but every attempt to write to redo log files fails with an error.