题目内容

开关柜交接试验，SF₆断路器交流耐压试验在SF₆气压为额定值时进行，试验电压按出厂试验电压的（）%。

A. 70
B. 80
C. 90
D. 100

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CREATE TABLE dept (deptno NUMBER(2), dname VARCNAR2(14), 1oc VARCNAR2 (13)); ROLLBACK; DESCRIBE DEPT What is true about the set? （）

A. The DESCRIBE DEPT statement displays the structure of the DEPT table.
B. The ROLLBACK statement frees the storage space occupies by the DEPT table.
C. The DESCRIBE DEPT statement returns an error ORA-04043: object DEPT does not exist.
D. The DESCRIBE DEPT statement displays the structure of the DEPT table only if there is a COMMIT statement introduced before the ROLLBACK statement.

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