8、Examine the statements that use flashback technologies:

1. FLASHBACK TABLE customers TO TIMESTAMP TO_TIMESTAMP(‘2013-02-04 09:30:00’, ‘YYYY-MM-DD HH:MI:SS’);

2. SELECT * FROM customers AS OF SCN 123456;

3. FLASHBACK TABLE customers TO BEFORE DROP;

4. FLASHBACK DATABASE TO TIMESTAMP TO_TIMESTAMP(‘2013-02-04 09:30:00’, ‘YYYY-MM-DD HH:MI:SS’);

5. SELECT * FROM customers VERSIONS BETWEEN SCN 123456 AND 123999;

6. ALTER TABLE customers FLASHBACK ARCHIVE;

Which set of statements depends on the availability of relevant undo data in the undo tablespace?

A) 1,3,6

B) 1,2,5

C) 3,4,5

D) 2,3,5,6

Answer：B

(解析：答案 6 是不依赖 undo，答案 3 也是不依赖 undo，使用排除法，正确答案是 B。)