Explanation/Reference:
E: A snapshot standby database receives and archives, but does not apply, redo data from a primary database.
D: Snapshot standby databases are best used in scenarios where the benefit of having a temporary, updatable snapshot of the primary database justifies additional administrative complexity and increased time to recover from primary database failures.
Note: Redo data received from the primary database is applied when a snapshot standby database is converted back into a physical standby database, after discarding all local updates to the snapshot standby database.
The data in the primary database is fully protected however, because a snapshot standby can be converted back into a physical standby database at any time, and the redo data received from the primary will then be applied.
Incorrect Answers:
A: A snapshot standby database receives and archives, but does not apply, redo data from a primary database.
References: https://docs.oracle.com/cd/B28359_01/server.111/b28294/manage_ps.htm