（355）When you're performing active database duplication, a backup of what kind is required?

A. A current RMAN backup-set backup is required.

B. No backup is required.

C. An RMAN image backup is required.

D. A manual backup is required.

E. A "duplicate" preparatory backup is required.

答案：（B）

解析：

可以直接复制一个活动的数据库而不需要任何备份。