291.ENCRYPT_TS is an encrypted tablespace that contains tables with data. Which statement is true
regarding the effect of queries and data manipulation language (DML) statements on the encrypted data
in the tables?
A. The data is decrypted during SORT and JOIN operations.
B. The data remains encrypted when it is read into memory.
C. The data remains encrypted when it is stored in the redo logs.
D. The data remains encrypted in the UNDO tablespace provided that the UNDO tablespace was created
with the encryption option enabled.
Answer: C
答案解析：
参考：http://docs.oracle.com/cd/E11882_01/server.112/e25494/tspaces.htm#ADMIN12327
To maximize security, data from an encrypted tablespace is automatically encrypted when written to the undo tablespace, to the redo logs, and to any temporary tablespace. There is no need to explicitly create encrypted undo or temporary tablespaces, and in fact, you cannot specify encryption for those tablespace types.