What is the implication of this command?（）
A. The command produces an error because the retention time cannot be reduced.
B. All historical data is retained but the subsequent flashback data archives are maintained for only three years.
C. All historical data is purged and the new flashback data archives are maintained for three years.
D. All historical data older than three years is purged from the flashback archive FLA1.&e
在JSP中如果要导入java.io.*包，应该使用（）指令。
A. page
B. include
C. forward
D. tagli
“天雨盐丁愁，天晴盐丁苦”，出自（）的“盐丁愁”，对当时山东盐丁生产及生活作了真切动人的描述。
A. 白居易
B. 管仲
C. 杜甫
D. 任宏远
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