Which two statements about switchover and failover are true?

Which two statements about switchover and failover are true?

A.
A snapshot standby can be the target of a switchover or fast-start failover operation.

B.
Neither a switchover nor a failover is possible to a far sync instance.

C.
For fast-start failover, you must preselect the target standby database that will be used.

D.
You can activate a standby database to test whether it is being updated correctly.